Cromemco Z -2D · 2019. 9. 27. · Microcomputermart Ltd., 29 Hanging Ditch, Manchester (061-832-2269) NewBear Computing Store, Bone Lane, Newbury, Berks (0635-49223) Xitan Systems

0 50p

actlcill13An ECC Publication. Volume 2 Issue 2 February 1979

Cromemco Z -2Dunder themicroscope

Microcomputersystems fordoctors andestate agents

Pet Corner

Putting payrollon a computer

Low-costperipherals

Afteryou've been chased

by rhinos and have met

the hangman ishOne lesson you'll have to learn on your

own - how to tear yourself away from yourcomputer in the early hours. Infoguide providesyou with a new concept in recreational,educational and business software.

Insert your Compusette,and there's theHangman to challenge.

Or Rhino -a progressively harder

chase through thejungle, where you're

never sure what'sgoing to happen next.

Insert other Compusettes, and ...

could see you takingyour computer on atMastermind.Or Go!

sees you and your computer workingon statistical programmes. Conversion.Financial management. Forecasting. These -and many other functional programs - areon Cornpusette.

why not simulate an enzyme reaction?Change any one (or more) of six parameters andsee what happens? Maybe discover, whenplaying chess, that your computer is a GrandMaster? A Compusette will supply each of thenecessary programs.An interesting variety of Compusettes are beingmade available for PET, Apple II and TRS 80.Each is accompanied by a fully detailed bookletwith listings of the programs - there are up tothree on each tape.You will find that most dealers handlingpersonal computers will be stocking theCompusette range. Ask you dealer now.For as little as £2.70 per program* - that's value!

SOMPIISETTESCompusettes are produced by Infoguide Ltd,142 Wardour Street, London W1.120 El Camino Drive, Suite 108, Beverley Hills, Cal 90212 USA

* Based on three programs on an £8.00 Compusette.

Circle No. 101

PracticialCompptmg

Managing Editor

Dennis Jarrett

Computabits EditorNick Hampshire

Production EditorHarold Mayes

Advertisement ManagerErica Gibson

Advertisement RepresentativeTom Moloney

Subscription ManagerAnnabel Hunt

Publisher

Wim Hoeksma

Company SecretaryCarole Fancourt

Managing DirectorRichard Hease

Editorial, Advertising andsubscriptions: 01-278 9517.

Practical Computing is publishedby ECC as a subsidiary ofWHICH COMPUTER? Ltd at itsregistered office, 2 DuncanTerrace, London, NI, and printedby Bournehall Press Ltd,Welwyn Garden City. Distributedby Moore Harness Ltd, 31 CorsicaStreet, London, N5.c Practical Computing 1978ISSN 0141-5433.

Subscription rates: Singlecopy: 50p. Subscriptions: U.K., £6per annum (including postage);overseas, £12 (including airmail

postage).

Every effort has been made toensure accuracy of articles and

program listing. PracticalComputing cannot, however,accept any responsibilitywhatsoever for any errors.

PRACTICAL COMPUTING February 1979

Contents

CROMEMCO REVIEW

We put the Cromemco Z2 -D under the micro-scope to test its capabilities.

Page: 31

SYSTEMS FOR ESTATE AGENTS& DOCTORS

A look at some of the systems available forholding either patient or property records andhow much they cost.

Page: 27

PROCESSING THE PAYROLL

Setting -up a payroll system is not so difficult.We report how you can do it for less than £1,000.

Page: 35

PET CORNER

A new monthly column which shows how usersare making the most of the Pet, with ideas foryou.

Page: 28

LOW-COST PERIPHERALS

The cost of visual display terminals and printersis one of the handicaps of buying a cheap system.We look at the problem.

Page: 38

BUYERS' GUIDE

Comprehensive guide to micros on the Britishmarket, with details of prices, configurationsand applications.

Page: 60

AND MUCH MOREComputabits looks at moving programs, bubblesorts, and games, page 67; Feedback, page 19;Printout, page 25; Micros at LongfieldSchool, page 40; Cambridge Computer Store,page 45; Warlock Warren-a game, page 46;Illustrating Basic, page 51; Standards for tapecassettes, page 59; Play noughts and crosses,page 65; Glossary, page 78.

3

SOUTHWEST TECHNICALPRODUCTS FOR 6800USERS

MP-68CPU, 4K RAM £3558K additional RAM £140560KB twin disk system £1,400160KB twin mini floppy system £860CT -64 V.D.U. upper/lower case, monitor £455PR -40 40 -column printer £250Cassette interface £100GT-61 Graphics Terminal £105

A favourite with schools and colleges -low priced system that can grow.

Attractive low-priced software!

FOR THE PROFESSIONAL- CROMEMCO

Z-2 system:fully assembled £575Z-2 system: Kit ... £395Disk system from.... . £1,425CS -3 System 3, 32K, dual disk,expandable £4,1754 MHZ Single card computer £345Bytesaver board with PROMProgrammer.. £13516K PROM card £135Analogue Interface. £135Disk - BASIC, FORTRAN,ASSEMBLER, COBOL, each -.....£85etc. etc...A rugged well -engineered system designed forhard use. Expandable to 512K,21 Boards.Excellent software support CP/M AVAILABLE

PROCESSORTECHNOLOGY SOL 20/16

Computer system, 16K, V.D.U. etc £1,785Additional memory, 16K dynamic ..1275Mini -floppy disk (first) £635High quality word processingprinter from £1,800

A quality 8080 based system.Over 7,000 sold! Excellent word processingsoftware available.

Also ... Printers for all the above systems ...extra software ... diskettes ... cassettes ...Chess Challenger 10 ... games ... etc....Branches in Nottingham, Tottenham Court Road

4

V VVVVVVVY V V Y Y YYVYYYvYyY Y Y yyyylYVVVYVYMY YV l'YYV

THE BYTESHOP V.D.U.16 x 64 DisplayUpper/Lower CaseSeparate KeyboardClear 7 x 9 Dot MatrixBritish Design & ManufactureCC1TTV24 or Currentloop interface £359VDU without keyboard .. ..... £299

BOOKS GALORE!Introduction to MicrocomputersVol. 0 £5.95Vol. 1. Basic Concepts £5.95Vol. 2. Some Real products. £11.95Some Common BASIC Programs £5.95Instant BASIC £7.50Understanding microcomputers £7.95Your Home computer £4.956800 Assembly language programming £6.95808A Assembly language programming £6.95Z-80 programming for logic design £5.95Pit. etc....Also most U.S. magazines available....Personal Computing, BYTE, Interface Age,Dr. Dobbs etc...

NORTH STAR COMPUTERPRODUCTS

Horizon -1 system, 16K, 1 mini floppy....£1,265Additional mini floppy. .. £325Additional 16K static memory 4MHZ £315Printer interface.. £70Extended BASIC and DOS included in above

Release 4 BASIC & DOS E25CP/M Horizon £130

A value -for -money systemusing the advancedZ-80 clip and 5100 Bus.

- London, Birmingham, Manchester & Glasgow.

COMMODORE SYSTEMS

Pet personal computer, including V.D.U.BASIC interpreter + 8K user memoryBuilt-in cassette, ready -to -go £643.52Pet 2nd cassette deck £55.00Pet software, large selection, from £3.00Joystick, video monitor attachment,now available!Expandor printer, Pet Interface andpower supply .£414.00A very popular and adaptable system,excellent value!KIM -1 system 2K ROM, 1K RAM etc. £149.00KIM -3 additional 8K RAM £179.00KIM -4 Motherboard £89.00KIM -5 Assembler and Editor.... ........ ..£129.00

IPlease send me

I(if preferred, attach order on separatesheet to coupon)

Name

IAddress

IL I enclose cheque for £El Please debit my Diners Club/

American Express/Access/BarclaycardAccount no

Please add 8% VAT to all items except books

The Byte Shop Ltd426-428 Cranbrook Road, Gants Hill,Ilford Essex. Tel: (01) 518 1414.All prices correct at time of going to Press

Circle No. 102PRACTICAL COMPUTING February 1979

comart

Comart's Cromemco systems representprobably the widest range of microcomputing power available today.Systems are in use in control,research, educational and commercialapplications: the S100 standard addsthe dimension of future compatibilityand expandability.

Contact us direct or call your nearest dealer.

* Single Card Computer* Z80A Z2 Computer* Mini & Standard Floppy Disks* PROM & 4MHz RAM cards* Analogue, Digital, VDU & Printer

interface cards* BASIC, FORTRAN IV, COBOL &

Macro -Assembler languages* Cromemco System Three

The Byte Shop, 426/428 Cranbrook Road, Ilford, Essex ((01-554-2177)Cambridge Computer Store, 1 Emanuel Street, Cambridge (0223-68155)Computerbits Ltd., 41 Vincent Street, Yeovil, Somerset (0935-26522)Holdene Ltd., 10 Blenheim Terrace, Woodhouse Lane, Leeds 2 (0532-459459)Isher-Woods, 110 Leagrave Road, Luton, Beds (0582-424851)Microcomputermart Ltd., 29 Hanging Ditch, Manchester (061-832-2269)NewBear Computing Store, Bone Lane, Newbury, Berks (0635-49223)Xitan Systems Ltd., 23 Cumberland Place, Southampton (0703-38740)

COMART LTD., PO BOX 2, ST NEOTS, CAM BS PE19 4NY. (0480-215005)

Circle No. 103PRACTICAL COMPUTING February 1979 5

ThegreatRAMsaleThe Nascom system offers major expansion at saleprices. To give you as much choice as possible we offerRAM boards in three configurations to accommodateup to 16 memory ICs of either MK4027 or MK4116,all socketed.

The memory board kit options are:8K £85.00

16K £140.0032K £200.00

Boards will also accommodate up to four EPROMS oftype 2708 at £10.50 plus VAT each. And if you wishto upgrade 16K to 32K it will only cost you anadditional £70.Memory boards plug straight into a NASBUS and anedge connector is included for this. All boards mustbe used in conjunction with the buffer board which,like the memory boards, is available in kit formex -stock from approved Nascom distributors.

121 High Street,Berkhamsted,Herts.

Tel: (04427) 74343

Nascom Microcomputers

Circle No. 104

EQUINOX 300A powerful multi-user

multi -taskingmulti -language

16 -bit microcomputer time-sharing system

supporting* BASIC* LISP' PASCAL" Floppy discs Hard discs

including a powerful Text Formatter,Assembly Language Development Systemand disc -based Sort utilities.

Priced from under £5,000

Write or phone for further information.

EQUINOX COMPUTER SYSTEMS LTD32-35 Featherstone Street,

London EC1Y 8QX.(Tel : 01-253 3781/9837)

Circle No. 105

Eu/uzi-CaLc Ltd224 TOTTENHAM COURT ROAD, LONDON Wl. TEL: 01-636 8161New Shop: 55-56 High Holborn, London WC1 Tel 01-405 3113

For electronic calculators andwatches.

We have the largest range inLondon at the mostcompetitive prices.

Export and Personal ExportTax, free facilities arranged.

HEWLETT PACKARD * CASIO* SHARP * TEXAS

INSTRUMENTS * OLIVETTI *SEIKO * SINCLAIR *

COMMODORE * SANYO *NATIONAL PANASONIC, ETC.

IWe stock the

COMMODOREPET 2001-8

APPLE II

NORTH STARHORIZON

and

TEXAS SR60a

microcomputers with a fullrange of hardware and

software options.

Circle No. 1066 PRACTICAL COMPUTING February 1979


THEBRITISHMICRO

RAI R BLACK BOXMICROCOMPUTER

High speed 8085 microprocessor

Priority interrupts and DMA

64K bytes of RAM memory

Transparent ROM bootstrap loader Integral dual minifloppy disks

Programmable serial I/O interfaces

Comprehensive range of peripherals

UK wide on -site maintenance

Advanced floppy disk operating system

Serial and random file processing

Macro assembler with symbolic debugging

Extended BASIC interpreter Relocating FORTRAN IV compiler

ANS 74 COBOL compiler

Quantity and OEM discounts

Leasing and rental facilities

MIR MIR MIR RAIR MIR MIR30-32 NEAL STREET COVENT GARDEN LONDON WC2H 9PS TELEPHONE 01-836 4663

Circle No. 1077

Computer standard IN

3A PSUComputers require a reliable and even power supply.The redesigned and uprated Nascom 3A PSU meetsthese requirements. Its output voltages are +5V 3A;+12V 1A; -12V 1A; -5V 1A. And are sufficient todrive the Nascom-1, buffer board and up to 32K ofRAM. It has LED displays on all the outputs and willfit into the Nascom frame to be announced soon.Price of PSU kit -£24.50 plus VAT.A buffer board kit with edge connectors suitable forthe NASBUS and with edge connectors and inter -connectors to attach directly to the Nascom-1 isavailable at £25.00 plus VAT.

A121 High Street,Berkhamsted,Herts.Tel: (04427) 74343

Nascom Microcomputers 1 Circle No. 108

The Magazine of the APPLE,KIM, PET and other

6502 Systems.Single issue £1.50 Subscription £7.50

Overseas Subscription £8.00

How to Order:In Sterling or U.K. Bank, by Cheque, P.O. orCredit Card made payable to:

L.P. ENTERPRISESRoom PC/J313 Kingston Road

Ilford, Essex IG1 1JP, U.K.Phone: 01-553-1001 for Credit Card order

(24 -hour service)

Circle No. 109

56 -STATION ASCII KEYBOARDNOW IN STOCK ASCII KEYBOARD MODEL KB756

KB756 mounted on PCB

ONL Y £49.50(mail order total £55.08)

KB756MF including metal mountingframe for extra rigidity,

ONLY £55.00 (mail order total £61.02)

SPECIAL PURCHASE OF SHINSHUSEIKI 21 -COLUMN ALPHANUMERICPRINTER MECHANISMS MODELAN101F

SELF -SCAN ALPHANUMERICPANEL DISPLAY

16/18 position display dimensions 8 '/." x 2 Vx"with 64 character repel- x 1 Y.". Supplied withtoire, 5 x 7 dot matrix. In- full technical data. Priceput 6 -bit BCD -code, £55.00 + 75p PEtP + 8%power requirements VAT (Mail order total+ 5v, -12v. Character size E60.21 I.0.40" x 0.28". Overall

Optional Extras:

KB15P Edge ConnectorKB701 Plastic EnclosureKB702 Steel EnclosureKB710 Numeric PadKB2376 Spare ROM Encoder

Continuous rotatingdrum device with 15VDC motor. 42 characterset of alphanumerics and symbols. Printing speed1.2 lines per sec. on standard 31/2" adding machineroll. Supplied with full technical manual.Dimensions: 6' x 41/2" x 61/2", weight: 3Kg.

Mail order totalAN101F Printer £45.00 £50.76Amphenol Connector f 3.50 £ 3.78

We also specialise in: DEC minis- PDPB and PDP11 processors, add-on memory,peripherals and spares. Hard copy terminals -ASR 33 and KSR 33 Teletypes, Data

Dynamics 390, Texas Silent 700. Send for complete lists.

ELECTRONIC BROKERS LTD.=.1 - 49-53 Pancras Road, London NW1 2QB.

Tel: 01-837 7781. Telex: 298694.

Mail OrderTotal

f 3.25 £ 4.05£12.50 £14.31£25.00 £28.62£ 8.00 £ 9.18£12.50 £14.04

HAZELTINE VISUAL DISPLAY UNIT* Teletype Compatible* 12" Diagonal Screen* TTY Format Keyboard* 12 lines of 80 characters* 64 ASCII Character Set* 5 x 7 Dot Matrix* Switch -selectable

Transmission Speeds upto 9600 baud

* Switch -selectable Parity* Standard CCITT V.24 Interface

+ carriageand VAT

Also available: -Model H-2000: Buffered/Editing model with direct cursoraddressing, dual intensity video, and detachable keyboard withseparate numeric and edit clusters. 27 lines of 74 characters.Price £495.00 + carriage + VAT.

A copy of trading conditions supplied on request

MODEL H-1000 PRICE £350

Circle No. 110/3 PRACTICAL COMPUTING February 1979

U.K. DISTRIBUTORSLtd.

Ardrossan, AyrshireComputerland, Ltd.Gerrards Cross, Bucks.

Leenshire, Ltd.Winchester, Hampshire

Sirton ProductsCoulsdon, Surrey(Airamco,

Computer CenterFleet, Hants.

Factor OnePenzance, Cornwall

Newbear Computing StoreNewbury, Berks.

TeleplayNew Barnet, Herts.

MEM-216K Static RAM Boards-i 00, fully buffered,with PHANTOM and bankaddressing capabilities,can be addressed at 4Kboundaries.

25Ons Kit45Ons Kit

250ns A&T450ns A&T

$285.00$250.00$350.00$325.00

EPROM BOARD KITSEPM-1 (uses up to 4 Kof 1702) $59.95JG8 /16 (uses 2708 or2716) $69.95

EXPANDOR'S BLACK BOX PRINTERThis 64 -character ASCII impactprinter with 80 -column capabilityis portable and uses standard8%" paper and regular typewriterribbon. Base, cover and parallelinterface are included. Assembledand complete with manual anddocumentation.

only $430.00(90 day manufacturer's warranty)

TRS-80 Interface Cable for Black Box Printerwith mating connectors: $48.00(must be used with expansion module, +8v/1 amp powersupply required).

Power Supply for TRS-80/Black Box Printer $49.00

TRS-80 afrIPPla "MEMORY EXPANSION KITS

4116's

8 for $85.00(16Kxl, 200ns)

includes dip plugs andinstructions

*TRS-80 Kit *(1 6Kxl, 300ns)

includes connectors andinstructions

$90.00

MICROPROCESSORS

F8Z80 12MHz)Z80A (4MHz)CDP1802CD6502680068028008-180358035-88080A8085TMS9900T L8080A SUPPORT DEVICES

8212821482168224 (2MHz)8224-4 (4MHz)822682288238USRT

S2350UARTSAY5-1013AAY5-1014ATR 16026TMS60111M6403BAUD RATE GENERATORSMC 1441114411 Crystal6800 PRODUCT6810P6820P6821P6828P6834P6850P6852P6860P6862P6871P6875P6880PKIM SUPPORT DEVICES

65026520652265306530-0026530-0036530-0046530-005CHARACTER GENERATORS2513 Upper 1-12+5)2513 Lower (-12T512513 Upper 15 v5102513 Lower 15 volt)MCM6571 up scanMCM6571A down scnPROMS

1702A27082716 15+12) TI2716 15y1 INTEL2758 (5v)DYNAMIC RAMS4160/4116 1250ns)2104/409621076-4TMS4027/4096 (300ns)STATIC RAMS

21 L02 (45Ons)21 L02 (25Ons)2101-12111-12112-1FLOPPY DISKCONTROLLERS1771601

KEYBOARD CHIPS

$16.95$20.00$25.00$17.95$11.95

25.0012.9520.00

$21.00$10.00$23.00$49.95

$2.90114.65

$9.95$2.75$6.40$6.40

$10.95

$5.25$8.25$5.25$5.95$9.00

$10.00$4.95

6.606.60

$11.25$16.95$8.65

$11.00$9.25

$12.00$28.75

$8.75$2.50

$11.95$10.00$9.25

$15.95$15.95$15.95$15.95$15.95

$6.75$6.75$9.75

$10.95$10.95$10.95

$8.00$9.95

$25.00$60.00$23.40

$12.50$4.00$3.95$4.00

1-15 16-100$1.50 $1.20$1.75 $1.50$2.95 $2.60$3.25 $3.00$2.95 $2.65

$39.95

AY5-2376 $13.75AY5-3600 $13.75

libMM5740 $18.00

Gook!DYNAMIC RAM BOARDS

EXPANDABLE TO 64K32K VERSION KITS

Uses 4115 (8Kx1, 250ns)Dynamic RAM's, can beexpanded in 8K increments upto 32K.

8K $199.0016K $255.0024K $310.0032K $369.0064K VERSION KITSUses 4116 (16Kx1, 25Ons)Dynamic RAM's, can beexpanded in 16K incrementsup to 64K.16K $292.0032K $432.0048K $578.0064K $721.00

* STATIC RAMSPECIALS

2114's,low power 11024x4)1-15 16-99 100 +

450ns 8.00 6.95 5.50250ns 9.00 8.00 6.50TMS4044/MM5257, low power450ns 8.00 7.50 6.50250ns 9.95 8.75 8.004200A (4Kx1, 200ns)

9.95 8.50 8.00

JADE 8080Awith full documentationKit $100.00Assm. & Tested $149.95Bare Board $30.00

S-100 MOTHER BOARDSJADE 6 -SLOTKit $41.95Assembled & Tested $56.95Bare Board $24.95

9 -SLOT "LITTLE MOTHER"Kit $85.00Assembled & Tested $99.00Bare Board $35.00

13 -SLOT "QUIET MOTHER"Kit $95.00Assm. & Tested $110.00Bare Board $40.00

22 -SLOT "STREAKER"Assm. & Tested $149.00

STATIC RAM BOARDSJADE 8K

Kits: 450ns $125.9525Ons $149.75

Assembled & Tested:450ns $139.7525Ons $169.75

Bare Board: $25.0016K Uses 2114'silow poweTAssembled & Tested:

RAM 16 (25Ons) $375.00RAM 16B(450ns) $325.00

16K with memory managementAssembled & Tested:

RAM 65 (250ns) $390.00RAM65B (450ns) $350.00

32K StaticAssembled & Tested:

25Ons $795.00450ns $725.00250ns Kit $575.00

.31A-3DOM Z80with provisions for ONBOARD2708 and POWER ON JUMP

2 MHzKitAssm. & Tested

4 MHzKitAssm. & TestedBare Board

$135.00$185.00

$149.95$199.95$35.00JADE

VIDEO INTERFACES-100 Compatible SerialInterface with Sockets Included.Kit $117.95Assm. & Tested $159.95Bare Board withmanual $35.00

FLOPPY DISK INTERFACEJADE FLOPPY DISK (Tarbellboard)Kit $175.00Assm. & Tested $250.00S.D. Computer Products"Versa Floppy"Kit $159.95Assm. & Tested $189.95

-3--ok.mbm PARALLEL/SERIALINTERFACE

S-100 compatible, 2 serialI/O ports, 1 parallel I/O.Kit JG-P/S $124.95Ass. & TestedJG-P/SA $179.95Bare Boardwith manual $30.00SA DM

Computer Products4901 W. ROSECRANS AVENUEDepartment "1.1-HAWTHORNE, CALIF. 90250U.S.A.

17 Mk Afelf RICAN0.33FIC SS (*-1

Telephone:(2131 679-3313Telex:18-1823

Discounts available at OEM quantities. All prices above are quotedU.S. $ F.O.B. Hawthorne, Calif., U.S.A. To expedite shipmentsplease include international money order or bankers check payableagainst any U.S. bank in U.S. $, or use your Barclay, Access orAmerican Express credit card (include card number, expiration date,and signature). Add 20% of total order for postage.

WRITE FOR OUR FREE CATALOGAll prices subject to change without notice.


-4.0911"

DISK DRIVESMINI DISK DRIVE $295.00Model B51 by Micro Peripherals,lnc.will operate in either single density(125KB, unformatted) or double den-sity (250KB, unformatted) modes, upto 40 tracks, with a track -to -trackaccess time of only 5ms.

SA801R $495.00Shugart single -sided 8 in. floppydisk drive.

DM 2700-S $750.00Includes SA801 R disk drive, 10 in. x10 in. x 16 in. cabinet, power supply,data cable, fan AC line filter.

VERBATIM FLOPPYDISKS

51/4 in. MinidiskettesSoft sector, 10 -sector,or 16 -sector$4.40 each or box of 10for $40.00

8 in. Standard FloppyDisks

Soft Sector$4.75 each

10 for $42.50 s#

Circle No. I I I9

One year,three seminarsand 12,000 kits later,

Nascom presents

FTPLIER-110115

Two one day seminars to be held inLondon in the Spring of 1979.

Day one will be on small businessapplications. Day two will bespecifically aimed at the personaluser.

Write for further details now.

11Nascom Microcomputers

121 High Street,Berk hamsted,Herts.Tel: (04427) 74343

Circle No. 112

KM£99 + VAT

COMPUTERBITSP.O. BOX 13, YEOVIL,

SOMERSET0935-26522

Circle No. 11310

cCJ

ELECTRONIC SERVICING LTD.

WANTEDGood Homes for Intelligent Pets

THE

PET 2001 Computer£64352 plus VAT

rexIllustrated: PET plus optional sound cassette

deck and printer (prices on application)

This unbelievably versatile, compact,portable and self-contained unit hasmany varied applications and offerstremendous benefits in the worlds of BUSINESS and COMMERCE:Can be used efficiently for Trend Analysis.Stock Control Payroll InvoicingInventory Control, etc. SCIENCE and INDUSTRY:The 'PET' has a comprehensive set ofscientific functions useful to scientists,engineers and industry. EDUCATION: An ideal tool forteaching and it can be used to keeprecords, exam results, attendancefigures, etc. ENTERTAINMENT: Gamesincluding Backgammon, Noughts andCrosses, Pontoon, Black Jack and MoonLandingPossesses all usual alphanumericsPLUS 64 graphic characters forplots, artwork, etc., a printer, 2ndcassette deck and softwareavailable AND IN THE NEARFUTURE 'Floppy Disc' data andprogramme storage system.We have six years' experience inservicing electronic calculators, mini-computers in S.E. England. 24 -hourservice contract available at £6950 perannum. Credit and leasing terms available.For full details and demonstrationcontact Peter Watts . . . Now!

STOP PRESSSee the full Tandy range

at our new shop inChertsey Road, WOKING

ELECTRONIC SERVICING LTD(Authorised Commodore Pet and Tandy Dealer) Specialistsin Electronic Servicing, Programming, Electronic Designand Prototype Manufacture

33 PORTUGAL ROAD, WOKING, SURREY GU2I 5JE

Tel: Woking (04862) 69032/68497/20727


IF YOU CAN'T BEAT THEM :-VECTOR GRAPHIC INC

VECTOR V18A slot Motherchassis accepts the wide range of VectorS100 cards and makes an ideal base to build a microcomputer system.Computing power is available to perform a wide range of tasks fromindustrial control to small business.

£350PR2 12K PROM/RAM card holds a comprehensive monitor programfor system testing and configuration. Normal operation is in conjunctionwith a serial terminal via I/O card.

£160FLASHWR ITER, memory mapped VDU with graphics, allows a system tobe built without a terminal or I/O card. Specify version EV of monitorprogram.

£150I/O, Switchable 110 to 9600 baud serial interface plus two 8 -bitparallel I/O ports.

£125High resolution graphics interface bit -maps 8K of RAM to 256 x 256points, or 128 x 128 with 16 level grey -scale.

£150

Z80 Processor card £140 8080 Processor card £1208K Static RAM 4MHZ £140 16K Static RAM 4MHZ £300Analogue Interface £70 Precision analogue interface £250Rackmount 18 slot motherboard £150 Rackmount power supply £90

8K Computer System £895

MICROPOLIS

Micropolis disk drives employ higher standards of engineering to packeither 143K or 315K bytes per diskette, formatted, Supplied completewith controller card, cables, manual and software they plug directlyinto the 5100 bus; 8080 or Z80.

Extended disc BASIC, mnemonic editor and assembler are provided, torun under the powerful MDOS operating system.

Add-on units are supplied to extend the system to four drives and onedrive per system may be powered from the 5100 bys.

143K System S100 powered £439 143K Add-on S100 powered £279143K System Mains powered £499 143K Add-on Mains powered £339

315K System 5100 powered £649 315K Add-on 5100 powered £349315K System Mains powered £699 315K Add-on S100 powered £399

Twin drive System 630K £1159 Twin drive Add-on 630K £859

5100 bus regulator £14 Diskettes per five £24

Unmounted drives available from £225

JOIN THEM !rIIIIMI=1.111,

VECTOR

MZ

Combining the best features of the VECTOR GRAPHIC computer and twinMICROPOLIS 315K byte drives. The Vector MZ produces, in one packagea powerhouse of Microcomputer ability.

The VECTOR PROM monitor bootstraps directly to either MDOS, forhousekeeping and Assembly language operation, or to BASIC to run high-leveluser programs. Provision is made to immediately attach a printer, forexample one of the extensive range from Centronics sold by Sintrom,enabling use of the powerful printer -related features in the MICROPOLISSoftware.

Applications Software for the VECTOR MZ now in preperation will performa wide variety of business functions; stock control, invoicing, ledger andmailing lists. Further applications exist as a microcomputerdevelopment system, and low cost replacement for minicomputer controland instrumentation.

£2300

VECTOR MZ configuration includes:

Twin disk 630K minifloppy.Full Micropolis disk software.Z80 4MHZ 32K processor.1 Serial port, 2 Parallel ports.12K PROM RAM card with extended monitor.

And will support:

Flashwriter, Graphics interface, Analogue interfaceAdditional RAM, additional minifloppy drives.

Centronics Microprinter £398Centronics 779 £780ADM3A VDU £620

PRICES EXCLUDE VAT

ALL EQUIPMENT FULLY ASSEMBLED AND TESTED

OEM AND DEALER ENQUIRIES WELCOME

DEMONSTRATIONS IN OUR SHOWROOM

SIN7ROM GROUP


Sintrom Microshop14, Arkwright Road,Reading, Berks. RG2 OLS.

Tel: Reading (07341 84322TELEX: 847395CABLES: SINTROM READING

Circle No. 115i

Written for the NascomAmong the programs written to run on the Nascom-1and available now are:

ICL Dataskil Letter EditorThis software provides a comprehensive set of dataoperations. Text can be input, displayed, edited,stored on tape, retrieved and further amended.Control functions include cursor, character, word, line,scrolling, tabbing, tape store and retrieve, textprinting. All in less than 2K byte plus workspacefor up to almost two full screens. Price on cassette£70 plus VAT.

TINY BASICA 2K BASIC Interpreter in 2x2708 EPROM. Normalcommands: 1-32767 MSL/single array/arithmeticconstant/<>-- = #/strings valid in print/listingdescription and user manual/additional three levelkeyboard control/compatible with NASBUG andB.Bug Price £25 Plus VAT.An extended version of the above is our TINY BASICPLUS which has all the TINY BASIC functions plusincreased operator manipulation in all sub -routines.Price in 3x2708 EPROM £35 plus VAT.

ZEAPAn editor assembler which runs under NASBUG andprovides the powerful advantages of writing programsin Z80 assembly language instead of directly in machinecode. Uses less than 3K bytes of memory and issupplied on cassette priced £30 plus VAT.

nmNascom Microcomputers

121 High Street,Berkhamsted,Herts.

Tel: (04427) 74343

Circle No. 116

AIRAMCO LTD - MICROCOMPUTER PRODUCTSDistributors for JADE, S. D. SALES, MATROX

All products brand new with full industrial specification

S100 COMPUTER CARDS KIT8100 Mother Board Kit 13 slots E71Jade 8080A CPU BOARD L75.00Jade Z80 CPU BOARD 2MHz £95.00Jade Z80 CPU BOARD 4MHz £99.95Jade Serial/Parallel I/O BOARD £89.95Jade 2708/2716 EPROM BOARD L44.95(16 x 2708 or 2716) WITH 8 2708s ...197.46Problem Solvers 16K STATIC RAM 450nS

16K STATIC RAM 250nSS. D. SALES. STARTER SYSTEM

Single -card computer systembased on Z80. Similar in appear.ance to KIM or D2 kit. IK RAMPROM programmers, 4 -channelcounter -timer, cassette interface,provision for 5100 L159.95 C249.95

VERSAFLOPPY DISK CONTROLLER (up to4 drives 51 or 8" LI 11.75 L165.00SHUGART 8" Drive 801R £355.005100 Desk Top Rack L225.00 £249.00Components2708 1024 x 8 EPROM £6.99 4116 I 6K x I DRAM2716 2048 x 8 EPROM L29.90 8 for

TEXTOOL 24 pinZERO FORCE SKIS £5.60(equivalent of above) T.I.1702 256 x 8 EPROM £4.852104 4906 x 1 DRAM L3.50

8 for £26.0021078-4 4096 x I DRAM L3.50

8 for L26.00MK 4118 STATIC RAM 1Kx 8 PIN

OUT same as 2708EPROM..LI6.50Note New Low Prices I6K Memory

(intel)

All Prices EXCLUDE VAT @ 8%.Trade discounts on QuantityPlease add £1.00 P&P for S100 itemsthen add VAT @ 8%.

24 -hr Ansaphone order service withACCESS or BARCLAYCARD.MAIL ORDER ONLY

BAREASSEMBLED BOARD

L82.50 £26.25£122.50 £22.50£135.00 £26.25L145.00 £26.25LI29.95 L22.50£82.46 L22.50

L134.96 £22.501210.00£296.00

£125.00

6821P PIAAY51013 UARTAY51014 UART (5V)AY53600 ENCODER8080A CPU21L02-1 450nS

8 for21L02 250nS

8 for21 12- 1 256 x 4 (450)4044 4K x I (450)4045 I K x 4 (450)

C10.50C75.00£5.90£4.50£6.50£9.99£8.99L1.20£7.92L1.40£9.60£2.25£7.45£8.25

For components please add 40 P&P,then add VAT @ 8%.AIRAMCO LTD30 WITCHES LINNARDROSSANAYRSHIREKA22 88RTEL. 0294 65530TELEX 779808

Semiconductor prices are alwayschanging and the trend is generallydownwards. So ring for latest up-to-date details.

Circle No. 117

THERE'S MORE TO LUTON THAN

CAMPARI AND THE AIRPORT

There's the Commodore PET, the APPLE II, the North Star Horizon, Processor Technology'sSol, Cromemco's Z2, Z2D and System 3. Together with disc drives and terminals and printersand VDUs and all manner of accessories and books and magazines. Almost everything thePersonal Computer lover could wish for. So put away the holiday brochures and comealong to-

I sher-woodsPERSONAL COMPUTER SYSTEMS

110 Leagrave Road - Luton - Tel (0582) 424851 - Just off the Ml.

With acknowledgements to David Dampen and Luton Airport.

Circle No. 118I2 PRACTICAL COMPUTING February 1979

HobbyistCommercial

ScientistEducation

for the first timeuser and the professionalcheck out the PET, the world'smost popular personal computer

* CAPABLE - just like a traditional computer.

* UNDERSTANDABLE - fast, comprehensive and powerful -BASIC is one of the easiest computer languagesto learn, understand and use. Machine languageaccessibility for the professionals.

* PERSONAL - easily portable and operated - just "plug in"and go. Unique graphics make fascinating displays.

* EXPANDABLE - built in IEEE -488 output, 8K RAM expandableto 32K, parallel user port 2nd. Cassette interface.

* SERVICEABLE - easily serviced - only 3p.c. boards all readillyaccessible.

Features of PETS extended BASIC includeInteger, floating point and string variables; A full set of scientific functions, Logicaloperators, Multi -statement lines. String functions, Left $, Right $, Mid $, Chr $,Val, Str $, Peek, Poke, Usr, Sys, to interface to memory and machine languagesubtrontines. Time of day variable.

Future Commodore developments * FLOPPY DISC * PRINTER* MEMORY EXPANSION * MODEM

Extensive software readily available.

Contact your nearest PET dealer, call today for a demonstration

In case of difficulty call COMMODORE SYSTEMS DIVISION360 Euston Road, London. Tel. 01-388-5702

AUTHORISEDPETCOMMODOREDEALERS

BristolSumlock Tabdown Ltd0272-26685

DerbyDavidson -Richards (Int) Ltd0332-366803

DurhamDyson Instruments0385-66937

GrimsbyAllen Computers0472-40568

GuildfordP.P.M.0483-37337

Hemel HempsteadData Efficiency Ltd0442-57137

LiverpoolDams Office Equipment Ltd051-227-3301

London W.C.2TLC World Trading Ltd01-839-3893

ManchesterCytek (UK) Ltd061-832-7604

Sumlock ElectronicServices061-228-3507

NewportG.R. Electronics Ltd0633-67426

Northern IrelandMedical & Scientific08462-77533

NottinghamBetos (Systems) Ltd0602-48108

ReadingC.S.E. (Computers)0734-61492

SouthamptonBusiness Electronics0703-738248

SouthamptonSymtec Systems Ltd0703-37731

Theme, OxonMemec Systems Ltd084-421-2149

WokingPetalect Ltd048-62-69032


Circle No. 11913

Approved Nascom UK DistributorsNascom-1 available at £197.50 plus VAT from:

Barrow-in-FurnessCamera CentreTel: 0229-20473

TorquayCC ElectronicsTel: 0803-22699

Egham Et ManchesterElectrovalueTel: 07843-3603

Glenfield, LeicesterEley ElectronicsTel: 0533-871522

London W2Henrys RadioTel: 01-723 1008

Oldham, Lancs

Lock DistributionTel: 061-652 0431

Chesham, BucksLynx ElectronicsTel: 02405-75151

Liverpool L2MicrodigitalTel: 051-236 0707

New Barnet, HertsComp ComponentsTel: 01-441 2922

GlasgowStrathandTel: 041 552 6731

BristolTarget ElectronicsTel: 0272 421196

Nascom Microcomputers

Circle No. 120

COMPUTER SYSTEMS LIMITED

"OWING TOTREMENDOUS

DEMAND we areable to extend

the f10 Discountoffer until March

12th 1979r

The new low cost VDU -Tangerine 1648(See page 16, ETI, Oct. '78 for feature details)

ORDERING INFORMATIONThe normal KIT price is £139.86, which includes postage,packing and insurance and VAT @, 8%. HOWEVER, as an in-troductory gesture we are discounting this price by £10,for all orders received postmarked BEFORE 12th March,1979.

If you require further information, send an A4 sized self-addressed envelope. If you wish to purchase a kit pleasesend a cheque or money order made payable to

TANGERINE COMPUTERSYSTEMS LIMITED

RIVERMILL LODGE, LONDON ROAD, ST. IVES,CAMBS. PE17 4BR

Tel. St. Ives (0480) 65666

MATROXFROM

SHELTONPRICE (1 off)

1. A LT-256**2E 256 x 256 S100 graphics card £284.002. ALT -2480E 24 lines of 80 characters S100 £213.003. MTX-816 Big characters 8 rows

16 characters per line £128.00

4. MTX-1632 Very clear characters 32 characters16 lines (SL version can besynchronised to TV picture) £162.00

5. MTX-A1/MTX-B1 Keyboard scanners and LED driverSingle chips direct connection toany CPU bus £28.00

SHELTON INSTRUMENTS LTD.,22/24 Copenhagen Street, London N1 OJD Tel: 01-2786273


TINTERPRISESRoom PC Ja

313 Kingston Road, Ilford,Essex, IG1 1PJ, England

From Adam Osborne AssociatesINTRODUCTION TO MICROCOMPUTERSVolume 0: The Beginners BookVolume 1: Basic ConceptsVolume 2: Some Real Microprocessors (without binder)Volume 3: Some Real Support Devices (without binder)Updating Subscriptions for Vol 2 and 3Updating Subscriptions for Vol 2. and 3Single issue of updating SubscriptionBinder (specify for Vol 2 or 3)6800 Programming for Logic Design8080 Programming for Logic DesignZ80 Programming for Logic Design8080A/8085 Assembly Language Programming6800 Assembler Language ProgrammingSome Common BASIC ProgramsGeneral Ledger (Available from late summer 1978)Payroll with Costing AccountingAccounts Payable & Accounts Receivable

£ 5.95£ 6.30f18.95£11.95£18.95 each£30.00 together£ 4.00£ 5.75£ 6.30£ 6.30£ 6.30£ 6.45£ 6.45£ 6.30£10.95£10.95£10.95

From Basic Software Library(from Scientific Research Instruments)Vol 1: Business and Games ProgramsVol 2: Maths, Engineering and Statistical ProgramsVol 3: Advanced Business ProgramsVol 4: General Purpose ProgramsVol 5: Experimenters Programs (General Purpose)Vol 6: Miniature Business SystemsVol 7: Chess/Medbil/WDPROC

£17.50£17.50£26.95£ 7.95£ 7.95f32.50£26.95

Your Home ComputerHow to Profit From Your Personal ComputerHobby Computers Are HereNew Hobby Computers

£ 7.95£ 5.50£ 3.95£ 3.95

TV Typewriter Cookbook by Don LancasterTTL CookbookCMOS CookbookIC Timer CookbookIC OP -AMP CookbookRTL CookbookZ80 Microprocessor HandbookZ80 Instruction Handbook

£ 7.50£ 7.50£ 7.95£ 7.50£ 9.50£ 4.25£ 7.50£ 3.50

Magazines: Back IssuesPersonal ComputingInterface AgeDr. Dobbs JournalComputer Music JournalPeoples ComputersBYTECreative ComputingCalculators & ComputersROMKilobaud73MICRO -6502 Journal £

1.752.251.752.501.752.251.751.751.752.252.251.50

HOW TO ORDER

Please note our prices include postageand packing, but not insurance, ifwanted add 12p for every £10 ofbooks ordered. Make cheques, PO'setc. payable to:-

L.P. Enterprises.CREDIT CARDS acceptedBARCLAYCARD VISA/ACCESSDINERS CLUB/AMERICAN EXPRESS

Phone: 01-5531001 for Credit Cardorders (24 -hour service)

From BYTE Publications Inc.Paperbytes:

Tiny Assembler for 6800 SystemsBar Code Loader for 6800, 8080, Z80 & 6502 Micros

Best of BYTE Volume 1

£ 5.75£ 1.75f 8 95

From Scelbi Computer Consulting Inc.6800 Software Gourmet Guide & Cookbook8080 Software Gourmet Guide & Cookbook8080 Programmers Pocket Guide8080 Hex Code Card8080 Octal Code Card8080 Guide and One 8080 Code Card8080 Guide and Both Code Cards

£ 7.95£ 7.95£ 2.25£ 2.25 2.25£ 4.20£ 6.00

Understanding Microcomputers & Small Computer Systems £ 7.95SCELBI 'BYTE' Primer £ 9.958080 Standard Monitor (In Book Format) £ 9.958080 Standard Assembler (In Book Format) £15.958080 Standard Editor (In Book Format) £ 9.958080 Galaxy Game £ 7.95Special Package: 8080 Assembler, Editor, Monitor £20.00

Best of MicroBest of Creative Computing Volume 1Best of Creative Computing Volume 2BASIC Computer GamesThe Colossal Computer Cartoon BookComputer -Rage (A Board Game)Artist and Computer

£ 5.50£ 6.95£ 6.95£ 5.50£ 3.95£ 6.95£ 3.95

Sybex: Introduction to Personal & Business Computing £ 4.95Sybex: Microprocessors from Chips to Systems by R. Zacs £ 7.95Sybex: Microprocessors Interfacing Techniques by R. Zacs £ 7.95Getting involved with your Own Computer £ 4.75Best of MICRO £ 6.95

Basic BASICAdvanced BASICInstant BASIC by Jerald R. BrownYour Home Computer by James WhiteMy Computer Like Me... When I speak

BASIC by Bob AlbrechtGames with a Pocket Calculator by Thaigarajan & Stilovitch £ 1.75Games, Tricks and Puzzles for a Hand Calculator by W. Judd £ 2.49A Practical Introduction to PASCAL POA

£ 6.50£ 6.00£ 7.95£ 7.95£ 2.75

From Peoples Computer CompanyReference Books of Personal & Home ComputingWhat to Do After You Hit ReturnDr. Dobbs Journal Volume 1

£ 4.95£ 8.95£10.00

Subscriptions start within 3 weeks.

MAGAZINES: SubscriptionsPersonal Computing (Twelve Issues Yearly)Interface Age (Twelve Issues Yearly)Dr Dobbs Journal (Ten Issues Yearly)Computer Music Journal (Four Issues Yearly)Peoples Computers (Six Issues Yearly)Kilobaud (Twelve Issues Yearly)Creative Computing (Twelve Issues Yearly)Calculators & Computers (Seven Issues Yearly)73 (Twelve Issues Yearly)BYTE (12 Issues Yearly)MICRO -6502 Journal

Magazine Storage box (holds 12 minimum)

U.K. OVERSEASPRICE PRICE

£16.00 £17.00£20.00 £20.50£13.00 £13.50£ 8.50 £ 9.00£ 8.00 £ 8.50£20.00 £21.00£16.00 £16.50£10.00 £10.50£20.00 £21.00£21.00 £21.00f 7.50 £ 8.50

£ 1.25

Send to address aboveIndicate Payment Method:

All Orders must be PrepaidTotal Enclosed

My cheque, P.O., I.M.O. is enclosed in Sterling on U.K. Bank

Charge to Barclaycard/Visa/Access/Diners/American Express

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Name

Address

Signature

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All publications are published in U.S.A. and shipped air -freight by L. P. Enterprises. In unusual cases, processing may exceed 30 days.

TRADE ENQUIRIES WELCOME


Circle No. 12215

PETSOFTWARE

Of all the microcomputer systems now available, theCommodore PET is the one best supported by software.

The widest range of programs is offered by one company-PETSO FT.

You will find a hundred programs in the new 12 -pagecatalogue, covering Business applications, ProgrammingAids, and some superb Games. Hers are just a few examples:

VAT £17.50 A package for small businesses. ConsultancyService available.

PAYROLL £25 A four program package providing aneasy method of pay computation and access to month -endand year end data. Update service available.

STOCK CONTROL 4 £12 Stores data on up to 150items per tape file rof rapid recall and amendment.

PERCENTAGE COSTING £49.50 A powerful methodof handling cost information, facilitating the study ofpercentage changes in total due to individual changes.

MICROCHESS £14 Play against the latest version ofour famous chess program. Excellent graphics.

ASSEMBLER/EDITOR £25 Translates assembly lan-guage programs into machine code for direct execution.

DATA FILE HANDLER £12 Provides a working filehandling structure to be used when writing your ownprograms.

MICRO TEXT EDITOR £15 Line oriented text editorfor word processing applications etc.

BRIDGE CHALLENGER £10 You and dummy playfour person Contract Bridge against the computer.

PET BASIC TUTORIAL £15 Let your PET teach youto program in Basic with our best-selling tutorial suite.

PET WORKBOOKS £15 Set of five professionallywritten workbooks covering all aspects of the PET.

For further details of these and the other ninety programsin our free catalogue, call or write to us today.

We also accept credit card orders over the telephone.

PetsoftMICROCOMPUTER SOFTWARE

PO Box 9, Newbury, Berks. RG13 1PBTel. 0635-201131 01-352 1100 Telex 8951672

PET is the trademark of Commodore

Circle No. 12316

THE TOTAL SOLUTION FROM

ALMARCOF COURSE!

Now Almarc & Vector Graphic offer the complete solutionto your computing needs for £2300.00* . . The Vector MZneeds only the addition of a V.D.U. and it's ready to go.Completely assembled and fully tested the Vector MZ Offersthe following features as standard:-* S -I00 bus* 4 MHz Z80A processor* 158 instructions* two quad density Micropolis floppies-over 630k bytes

on line* serial port* two parallel ports* 32K static ram* I2K prom/ram board with extended monitor* Extended disc BasicSimply connect your peripherals (Elbit V.D.Us &Centronics printers are available from Almarc) and your upand running and, because the MZ uses the S -l00 bus, youcan plug in a massive range of add on units.Ring or Write for a demonstration to:-

Almarc Data Systems Ltd.,29 Chesterfield Drive,Burton Joyce,Nottingham. Tel: 0602 248565.

* Discount terms available.

Circle No. 124

TRS-80HARDWARE - SOFTWARE - MODIFICATIONS

If it's new. Hardware, Software, Plug-in Units orInformation:- We are importing, selling, writing ormanufacturing it for the TRS-80.

OUR SPECIALITY-WORD PROCESSING

If you are into writing and you haven't writtenwith the TRS-80 Electric Pencil, you haven't lived !The package includes lower-case and theRS232 20ma interface.

S100 Motherboards, Digitiser Kits, Plug-in Joy-sticks, 16K Memory Kits and a wide range ofAmerican Software. We are the European dis-tributors for theTRS-80 COMPUTING newspaper.Phone or SAE for information or Software list.

***** 00 ******:0

500

1 Strawberry Vale, Twickenham. Middlesex.Telephone: 01-892-8455


THE EXPANDABLE GENERAL-PURPOSE MICROCOMPUTER

PING FACTOR-,

THE 3802 ALSO HPS GRAPHICS

lau can us. the. for siulatfon..-

THE RESEARCH MACHINES 380ZA unique tool for research and education

Microcomputers are extremely good value. The outright purchaseprice of a 380Z installation with dual mini floppy disk drives, digitalI/O and a real-time clock, is about the same as the annual mainten-ance cost of a typical laboratory minicomputer. It is worth thinkingabout!The RESEARCH MACHINES 380Z is an excellent microcomputer foron-line data logging and control. In university departments ingeneral, it is also a very attractive alternative to a central main-frame. Having your own 380Z means an end to fighting the centraloperating system, immediate feedback of program bugs, no morequeueing and a virtually unlimited computing budget. You canprogram in interactive BASIC or run very large programs usingyour unique Text Editor with a 380Z FORTRAN Compiler. If youalready have a minicomputer, you can use your 380Z with a floppydisk system for data capture.What about Schools and Colleges? You can purchase a 380Z for yourComputer Science or Computer Studies department at about thesame cost as a terminal. A 380Z has a performance equal to manyminicomputers and is ideal for teaching BASIC and Cesil. For ALevel machine language instruction, the 380Z has the best softwarefront panel of any computer. This enables a teacher to single-stepthrough programs and observe the effects on registers and memory,using a single keystroke.

WHAT OTHER FEATURES SET THE 380Z APART?The 380Z with its professional keyboard is robust, hardwearingequipment that will endure continual handling for years. It has an in-tegral VDU interface-just plug a black and white television into thesystem in order to provide a display unit-you do not need to buya separate terminal. The integral VDU interface gives you upper andlower case characters and low resolution graphics. Text and graphicscan be mixed anywhere on the screen. The 380Z also has an integralcassette interface, software and hardware, which uses named cassette

files for both program and data storage. This means that it is easyto store more than one program per cassette.Owners of a 380Z microcomputer can upgrade their system toinclude floppy (standard or mini) disk storage and take full advantageof a unique occurence in the history of computing-the CP/MTMindustry standard disk operating system. The 380Z uses an 8080family microprocessor-the Z80-and this has enabled us to useCP/M. This means that the 380Z user has access to a growing body ofCP/M base -software, supplied from any independent sources.380Z mini floppy disk systems are available with the drives mountedin the computer case itself, presenting a compact and tidy installa-tion. The FDS-2 standard floppy disk system uses double -sided diskdrives, providing I Megabyte of on-line storage.Versions of BASIC are available with the 380Z which automaticallyprovide controlled cassette data files, allow programs to be loadedfrom paper tape, mark sense card readers or from a mainframe. Adisk BASIC is also available with serial and random access to disk files.Most BASICs are available in erasable ROM which will allow forperiodic updating.If you already have a teletype, the 380Z can use this for hard copy orfor paper tape input. Alternatively, you can purchase a low cost380Z compatible printer for under £300, or choose from a range ofhigher performance printers.*CP/MTM Registered trademark Digital Research.

380Z/I6K System with Keyboard £965.00380Z/56K complete with DUAL FULL FLOPPY DISK SYSTEMFDS-Z £3,266.00

380Z Computer Systems are distributed by RESEARCH MACHINES,P.O. Box 75, Chapel Street, Oxford. Telephone: OXFORD (0865)49792. Please send for the 380Z information Leaflet. Prices do notinclude VAT @ 8% or Carriage.

Circle No. 126PRACTICAL COMPUTING February 1979 17

This Is TheFamous

PLUS 8% V.A.T.

Stop reading about computers and get your hands on one! WithELF II and our new Short Course by Tom Pittman, you can mastercomputers in no time at all! ELF II demonstrates all 91 com-mands an RCA 1802 can execute and the Short Course quicklyteaches you how to use each of the 1802's capabilities.

Elf Irs video output lets you display an alphanumeric readoutor graphics on any TV screen or video monitor and enjoy thelatest video games.

But that's not all. Once you've mastered computer funda-mentals, ELF II can give you POWER with add-ons that areamong the found anywhere. American IEEEchapters plus hundreds of universities and major corporationshave chosen the ELF II to introduce their students and personnelto microprocessor computing!

Learn The Skill That May Soon Be FarMore Important Than Your College Degree!

The ability to use a computer may soon be more important toyour earning power than a college degree. Without a knowledgeof computers, you are always at the mercy of others when itcomes to solving highly complex business, engineering, industrialand scientific problems. People who understand computers cancommand MONEY and to get in on the action, you must learncomputers. Otherwise you'll be left behind.

ELF II Is The F -A -S -T Way to LearnComputer Fundamentals!

Regardless of how minimal your computer background is now,you can learn to programme a computer in almost no time at all.That's because Netronics has developed a special Short Courseon Microprocessor And Computer Programming in non -technicallanguage that leads you through every one of the RCA COSMAC1802's capabilities so you'll understand everything ELF II can do.

and how to get ELF II to do it!All 91 commands that an 1802 can execute are explained to

you, step-by-step. The text, written for Netronics by Tom Pittman,is a tremendous advance over every other programming book inprint.

SPECIFICATIONSThe £99.95 ELF II computer features an RCA

COSMAC COS/MOS 1802 8 -bit microprocessor

addressable to 64K bytes with DMA, interrupt,16 registers, ALU, 256 byte RAM expandable to

64K bytes, professional hex keyboard fully

decoded so there's no need to waste memorywith keyboard scanning circuits, built-in power

regulator, 5 slot plug-in expansion bus (less

connectors), stable crystal clock for timing

purposes and adouble-sided, plated-through pc

board plus RCA 1861 video IC to display any

segment of memory on a video

monitor or TV screen along with allthe logic and support circuitry youneed to learn every one of the RCA

1802's capabilities.

ELF IIomputer

Keyed specifically to the ELF II, it's loaded with "hands on"illustrations. When you're finished, ELF II and the 1802 will nolonger hold any mysteries for you.

In fact, not only will you be able to use a personal computercreatively. you'll also be able to understand computing articles inthe technical press.

If you work with large computers, ELF II and our short Coursewill help you to understand what makes them tick.

A Dynamite Package For Just £99.95 Plus 8% VA.T. IWith ELF II, you learn to use machine language - the funda-mental language of all computers. Higher level languages such asFORTRAN and BASIC must be translated into machine languagebefore a computer can understand them. With ELF II you build asolid foundation in computers so you'll really know what you'redoing, no matter how complicated things get.

Video output also makes ELF II unique among computersselling such a low price. Attached to your TV set, ELF II becomesa fabulous home entertainment centre. It's capable of providingendless hours of fun for both adults and children of all ages! ELFII can create graphics, alphanumeric displays and fantastic videogames.

Only a low cost RF modulator is required to connect ELF II toyour TV's aerial socket I (To order see below.)

ELF II's 5 -card expansion bus (connectors not included) allowsyou to expand ELF II as your needs for power grows. If you're anengineer or hobbyist, you can also use ELF II as a counter, alarm,lock, thermostat, timer, or for countless other applications.

ELF II Explodes Into A Giant)Thanks to ongoing work by RCA and Netronics, ELF II add-onsare among the most advanced anywhere. Plug in the GIANTBOARD and you can record and play back programmes, editand debug programmes, communicate with remote devices andmake things happen in the outside world. Add Kluge Board toget ELF II to solve special problems such as operating a morecomplex alarm system or controlling a printing press. Add 4kRAM board and you can write longer programmes, store moreinformation and solve more sophisticated problems.

Expanded, ELF II is perfect for engineering, business, industrial,scientific and personal finance and tax applications. No othersmall computer anywhere near ELF II's low price is backed bysuch an extensive research and development programme.

The ELF -BUG Monitor is an extremely recent break-through that lets you debug programmes with lightening speedbecause the key to debugging is to know what's inside theregisters of the microprocessor and, instead of single steppingthrough your programme, the ELF -BUG Monitor, utilisingbreak points, lets you display the entire contents of the registerson your TV screen at any point in your programme. You find outimmediately what's going on and can make any necessarychanges. Programming is further simplified by displaying 24bytes of RAM with full address, blinking cursor and auto scrolling.A must for serious programmers!

Netronics will soon be introducing the ELF II Colour Graphics& Music System - more breakthroughs that ELF II owners willbe the first to enjoy!

Now BASIC Makes Programming ELF 11 Even Easier!Like all computers, ELF II understands only "machine language" -the language computers use to talk to each other. But, to makelife easier for you, we've developed an ELF II Tiny BASIC. Ittalks to ELF II in machine language for you so that you canprogramme ELF II with simple words that can be typed out on akeyboard such as PRINT, RUN and LOAD.

"Ask Not What Your Computer Can Do ...But What Can It Do For YOU!"

Don't be trapped into buying a dinosaur simply because you canafford it and it's big. ELF II is more useful and more fun than "bigname" computers that cost a lot more money.

With ELF II, you learn to write and run your own program-mes. You're never reduced to being a mere keypunchoperator, working blindly with someone else's predevelopedsoftware.

No matter what your speciality is, owning a computer whichyou really know know how to use is sure to make you a leader.ELF II is the fastest way there is to get into computers. Orderfrom the coupon below,

H.L. AUDIO LTD., Dept. P.C., 138 Kingsland Road, London E2 8DY

NOW AVAILABLE FOR ELF II -

CI Tom Pittman's Short Course On Microprocessor & ComputerProgramming teaches you just about everything there is to knowabout ELF II or any RCA 1802 computer. Written in non -technicallanguage, it's a learning breakthrough for engineers and laymenalike. £5.00* post paid!O Deluxe metal cabinet with plexiglas dust cover for ELF II.£29.95. plus £1.50 p&p.O RF Modulator for use with TV set. £3.00* post paid.O GIANT BOARD kit with cassette I/O, RS 232-C/TTY I/O,8 -bit P I/O, decoders for 14 separate I/O instructions and asystem monitor/editor. £39.95* plus £1.00 p&p.O Kluge (Prototype) Board a,cepts up to 36 IC's. £17.00 plus50p. p&p.CI 4k Static RAM kit. Addressable to any 4k page to 64k.£89.95* plus 50p. p&p.0 Gold plated 88 -pin connectors lone required for each plug-inboard). £5.70* post paid.O Professional ASCII Keyboard kit with 128 ASCII upper/lowercase set, 96 printable characters, onboard regulator, parity, logicselection and choice of 4 handshaking signals to mate withalmost any computer.£6495° post paid.

CI Deluxe metal cabinet for ASCII Keyboard. 09.95* plus £1.50p&p.O ELF II Tiny BASIC on cassette tape. Commands includeSAVE, LOAD, ±, x, ÷, 1 I. 26 variables A -Z, LET, IF/THEN. INPUT,

SEND TODAY!

PRINT, GO TO, GO SUB, RETURN, END, REM, CLEAR, LIST,RUN, PLOT, PEEK, POKE. Comes fully documented and includesalphanumeric generator required to display alphanumericcharacters directly on your TV screen without additionalhardware. Also plays tick-tack-toe plus a drawing game that usesELF II's hex keyboard as a joystick, 4k memory required. £14.95*post paid.10 Tom Pittman's Short Course on Tiny BASIC for ELF II.£5.00* post paid.O Expansion Power Supply (required when adding 4k RAMI.£19.95* plus £2.00 p&p.O ELF -BUG Deluxe System Monitor on cassette tape.Allows displaying the contents of all registers on your TV at anypaint in your programme. Also displays 24 bytes of memory withfull addresses, blinking cursor and auto scrolling. A must for theserious programmer! £1495 post paid.Coming Soon: A -D, D -A Converter, Light Pen, Controller Board,Colour Graphics & Music System ... and morel

Call or write for wired prices!

H. L. AUDIO LTD.. Dept. P.0138 Kingsland Road, London E2 8DY(Tel 01-739 1582)Sole European Distributors for Netronics R & D Ltd., U.S.A.

Vest I want to run programmes at home and have enclosedO £109.58 including postage and V.A.T. for RCA COSMACELF II kit, 0 £5.94 including postage and V.A.T. for power

supply (required), 0 £5.95 for RCA 1802 User's Manual0 £5.95 including postage and V.A.T. for Short Course onMicroprocessor Computer Programming.0 I want mine wired and tested with power supply. RCA1802 User's Manual and Short Course included for just£164.10 including postage and V.A.T.0 I am also enclosing payment (including postage and V.A.T.)for the items checked at the left.

Total Enclosed £

USE YOUR 0 ACCESS 0 BARCLAYCARD

Account No.

Signature Exp. Date

CREDIT CARD PHONE ORDERS ACCEPTED 01-738 1582

Print Name

Address

DEALER INQUIRIES INVITED


Feedback

Our Feedback columns offer readers the opportunity of bringing their computing experienceand problems to the attention of others, as well as to seek our advice or to make suggestions,which we are always happy to receive. Make sure you use Feedback - it is your chance tokeep in touch.

Seeking three answersAM in the initial stages of trying to

acquire a personal computer, for serioususe rather than game -playing, and needthe answers to three questions. I am notsure if they come within the scope of youradvice offer:Where can I find information about what

facilities the CP/M operating systemoffers? CP/M seems to be much referredto as a "good thing" but no-one givesdetails.

I will need eventually more than 64Kbytes of store; if bank switching is used,can parts of store belong to more thanone bank? Or if not, how does onecommunicate from bank to bank?

Using some form of assembler, ratherthan Basic, are there any figuresavailable for how well the Z80, 6800and 6500 make use of program store?This will be a major cost item andshould be used efficiently.

W. StonesWokingham, Berkshire

CP/M really is a good thing. It is froma U.S. software house, Microsoft, whichsells it to equipment vendors. You couldprobably try some of them e.g., Rair (tel.no. 01-836 4663) who have it on theirBlack Box, or Micro Focus (01-727 5814)which has Cobol running under CP/M.There its also an embryonic CP/M Users'Group being run by our ComputabitsEditor, Nick Hampshire. If you wantmore information write to him, care of us.

Sadly we do not understand what you meanby "bank switching". Presumably you arelooking for a way to address more than64KB with an 8 -bit micro, in which casewe do not know of any which can do itsimply.

We cannot help you on your use -of -memory question, either.

Schools should be criticalCONCERNING your review of the 380Zmicro in the December issue. For asystem which claims to be suitable foreducation use, several important pointswere omitted. It surely must be admittedthat a single -user system is inadequatefor a class of, say, 20 0 level students, soshould we not be concerned with themulti-user system?

In particular, does it allow data files,multi-user assembler language, and whatsize of program can be used by eightusers simultaneously? It seems reasonableto the CSE student that if programs canbe listed on the printer, then so canresults. Is this the case?

As one involved in computer education,

it seems to me that schools should berather more critical of micro systems, andexpect the standards of software availableon the mini systems of five years ago.

I hope that the "wet blanket" natureof my letter will not affect its printing inan excellent magazine. Surely we musthave pros and cons.

M. ParrWombwell, Barnsley,

S. Yorkshire

Versatile mailing listRE mailing programs, page 17 of theDecember, 1978 issue. We run an SWTPCM6800 with 24K RAM and a MSI FD8disc system. We have a mailing list of1,000 addresses, each of which is in one of15 categories of priority and of 12separate geographical locations.

The program is run for a ModelASR43 printer with gummed labels. Asample run shows the versatility we havebeen able to build in. It is possible toselect labels for any one or more of thecategories in any of the regions or all.

For anyone interested we would bepleased to give further details.

S. J. ChatfieldCamborne, Cornwall

Calling users of PDP -11I SHOULD be much obliged if, throughPractical Computing, you could make itknown that I am trying to start a PDP/LSI-11 users' group. Despite some pub-licity already, there is still only littlesupport for the group. What I am tryingto do is to form a basis for interchange ofideas, expertise and even software forPDP-11 users.

I would be interested to hear fromanyone who uses a PDP-11 of any con-figuration, running under any operatingsystem for any application. Since Digitaltells us that it has sold 50,000 PDP-11sso far, there must be many peopleinterested, and hopefully many of themread your magazine.

P. C. Harris119 Carpenter WayPotters Bar, Herts.

Do you want to bean author?WE are a small but expanding publisherof technical text books. Our maininterest is to publish a series of booksrelated to computer applications the firstbeing our Computer Programs That Work

by Lee, Beech and Lee. This sold out afteronly eight months with the pleasantresult that it is now being re -printed.

There is clearly a market for books suchas this, based heavily on program listingswith short descriptions. As our first bookwas orientated towards science andgames, we are now interested in the non -science areas of business, information,linguistics and the like.

Other than that, our only requirementis that popular programming languagessuch as Basic in a widely -used dialect areused by our authors.

If your readers would like to share inour success, perhaps they could write tome with details of their ideas.

D. G. BeechSigma Technical Press23 Dippons Mill Close

TettenhallWolverhampton

Services on offerCONGRATULATIONS on an excellent maga-zine. I note that in both the November andDecember Feedback columns, there havebeen readers enquiring for mailing pro-grams. My company can offer compre-hensive mailing services which are usedwidely by auctioneers, art dealers, tradeunions, mailing houses and trade associa-tions.

D. M. TaylorNorth LincolnshireData Services Ltd.

RothwellLincoln

Where are thosediscounts?CONGRATULATIONS on a superb magazine;it is very informative. Your article oncomputing in schools is an illustration ofwhat my friend and I would like to happento our school, Liskeard Comprehensive. Iwant to make my career in computing-both hardware and software interests me-but I have no way of getting hands-onexperience with a computer.

My friend and I approached the head-master, who said a computer wouldprobably be purchased by the school inabout two years' time.

In two years time I will be at college. Irealise the great potential of a computer atschool, but I and others cannot make theschool appreciate the point. The optionsform for lessons which I received at the

(continued on page 21)

PRACTICAL COMPUTING February 1979 19

CI a day keepsyour Apple in play

Over a 5 -year period our lease/E purchase rates are as follows:

16K machine will cost you£25.47 per month



g - At the end of this time you willown the machineSend for details

PADMEDE COMPUTER SERVICESThe Tuns, High Street, Odiham,

Nr Basingstoke, Hants.Tel: Odiham (025-671) 2434

Circle No. 128

EQUINOX 300A powerful multi-user

multi -taskingmulti -language

16 -bit microcomputer time-sharing system

supporting* BASIC* LISP* PASCAL* Floppy discs

Hard discs

including a powerful Text Formatter,Assembly Language Development Systemand disc -based Sort utilities.

Priced from under £5,000

Write or phone for further information.

EQUINOX COMPUTER SYSTEMS LTD32-35 Featherstone Street,

London EC1Y 8QX.(Tel: 01-253 3781 /9837)

Circle No. 129

A more interesting way to learnwhat is amicroprocessor?

If you are considering buying a Microcomputer,Development System, or just want to learnmore about this exciting technology, then thisshort introduction to Microprocessors is foryou. Comprising a 72 page book keyed to overtwo hours of cassette tapes, the many aspectsof Microprocessors are explained, includingBinary and Hexadecimal counting. Internalstructure. Operation. Programming Tech-niques. Devising a program, etc... Learn atyour own pace with this valuable addition toyour reference library.

rTo Technical Book Services ORDER FORM -1PO. Box 79Maidenhead, Berks SL6 2EG

Please send me copy/copies of What is a microprocessor?0E10 75 each inclusive. I enclose remittances

Name(Print Please)

Address

Registered office 21, Mincing Lane, London EC1 Registered No12225

I

m Ciprcle No. 130

20 PRACTICAL COMPUTING February 1979

Feedback

(continued from page 19)

end of the third year had ComputerStudies on it; soon the course was can-celled through lack of pupils and theyalso do not have a computer.

My aim is to try to get the school topurchase a worthwhile piece of equipmentat a relatively low cost. For this I need alist of most of the possibilities of a com-puter in school and also prices and detailsof educational discounts. Can you help ?

R. J. FiddickWest Looe

Cornwall You probably will not secure any"educational discounts" from anyone ifyou are talking about a smallish system.Most of the small computer vendors areselling them hand over fist and do not needthe extra business. Discounts may beoffered by suppliers of bigger and moreexpensive micro systems, where the priceis likely to be more than £2,000.

On the other hand, £800-000 will buy aready -to -go Pet or Tandy; £500 will buya decent micro kit, plus a keyboard andcassette for use with a TV set.

These are not impossible sums, after all,it is only £10 each from 80 willing parents.If the school has a parent -teacher associa-tion, you ought to suggest it. We haveheard of school children raising cash forcomputers by running jumble sales, spon-sored walks and dances.

One good ploy we have come across isdoing advance deals on business systemssoftware; you approach local shopkeepersand small businesses and promise to writeand run some fairly simple programs forthem when you get your computer. Theypay something in advance, of course.

Typical applications for this would bemaintaining customer records, perhapsstock records, mailing lists and simplepersonalised form letters. For this youmight also be able to interest your localeducation authority, if it has any kind ofBusiness Studies programme.

Choice for a collegeTHIS college is considering the purchase ofa microprocessor -based computer system.The large range of systems available, how-ever, makes us concerned that we makethe right choice. Although not exactlynovices in the computer world, we are cer-tainly not experts and we find some dif-ficulty in deciding on a system which willbest serve our needs.

The college workload is largely com-mitted to the scientific and commercefields and any system we purchased wouldbe expected to serve both, and also be ofuse in the routine data processing asso-ciated with college administration.

Since our budget is in the region of£3,000, we cannot hope to satisfy our ulti-mate aims at once but we would like topurchase a "starter" system which would

be immediately beneficial to the collegeand capable of future expansion.

Briefly, then, we envisage a final systemwhich could support eight simultaneoususers, provide enough computer "power"to enable 0 and A level computer sciencecourses to be run, and have enough flex-ibility to run typical commercial applica-tions. Within this framework we haveisolated a number of features which wefeel are essential for any starter system.Thus:Memory: As much as we can get for

our money-about 32Kexpandable as the casharises.

Discs: A floppy disc system.Tape: Magnetic tape for program

and data storage (and tocompare disc/tape methods).

Printer: Matrix or line printer forrapid printing.

Languages: Basic, with the option of pur-chasing Fortran and Cobolcompilers at a later date.

The Buyers Guides in your magazinehave been of immense use to us and,together with our own investigations, sug-gest that the following computers couldform the nucleus of the system we need:

Cromemco (System 2 and Z2), Hori-zon, Sol 20/16, Pet, Compelec Altair Sys-tem 1300*, Computer Workshop System2, Rair Black Box*, Research MachinesLimited 380Z*, SEED MS1 6800, TandyTRS 80.

Those which seem of particular interestto us have been asterisked. It is at thispoint that the main problem arises. Sincewe have no familiarity with any of thecompanies, we find it difficult to make achoice. Consequently we have turned toFeedback in the hope that your experienceand that of your readers can help cut somepath through the micro jungle.

Problems such as ours must be commonamong schools and colleges entering themicro field and we are sure many areexamining some of the systems we havementioned. Your comments and advicewould therefore be warmly received.

D. SheppardDepartment of Science

Barry College of Further EducationBarry, South Glamorgan

We have written to Mr Sheppard withour opinion. Anyone with further ideas orexperiences of the machines listed may liketo contact him to pass on their experiences.

Stock control problemI SEE from Feedback in the Novemberissue that advice on systems is available.Could you, therefore, please advise me onthe following?

I am looking for a system which couldprovide stock control initially for 2,000items but which could be increased whennecessary by the addition of more units-

price around £500-£700, either ready -built or be assembled.

M. PageBushmills

Co. Antrim Do you mean stock control or stockrecording? If it is stock control you will findit difficult to implement it on a system inyour price range. The two which spring firstto mind are the Pet and the Tandy, both ofwhich have some stock control/recordingprograms developed.

You should really be looking for a systemcosting around £2,000, many of which youwill find listed in our Buyers' Guide. If youthink about it, purchasing a £2,000 systemwould probably cost you about £20 a week,which might well be worthwhile-and it istax-deductible if you are in business.

Incidentally in next month's issue weshall be examining systems available forstock control.

Computer coursesCAN YOU please suggest computer coursesfor two of our staff? The first problemthey have to solve is to identify the mostsuitable computer for our purpose. Theywould be required to program and serviceas necessary.

Hodges & Moss LtdShrewsbury

Salop We don't usually like to recommendcourses. Our sister magazine,WHICH COMPUTER? has, however,recently reviewed such a course and wasfavourably impressed. It was called Buyinga Computer and was run by AccountantsWeekly Courses, tel 01-402 4503. Youmight also like to contact the NationalComputing Centre which offers advice tonew purchasers of computers. Tel 061-2286333.

Anyone for chessI AM looking for a computer system foraround £200. My main interest is com-puter chess. Do you know if there areany micros which are helpful in this area.Do you think that for a cheap system afull qwerty keyboard is necessary. I havemy eyes on a 6800 but I have also heardof a 6809 system. Can you tell me any-thing about it?

Robert DavisLondon WC1

Our Buyers Guide details systems likethe Kim, Sym and Nascom all of whichare within your price bracket and could beprogrammed to play chess. There is alsothe Chess Challenger which is a dedicatedchess machine available at many toy shopsfor around £200. If you could spend a bitmore money the Pet and Tandy both havevery good chess programs which, we admit,have beaten us. As for the 6089, sadlywe don't have much knowledge. Can anyreaders advise?


The Age of Affordable PersonalComputing Has Finally Arrived

Ohio Scientifics

Superboard IIFull 8K basic and 4K user RAMBuilt and tested £263.84

Plus 8% VAT (includes delivery)

Superboard I I was designed specifically with lowprice and the first-time user in mind. It promisesto be the most dramatic price and performancebreakthrough to date, in the microcomputerindustry. Ohio Scientific, with headquarters inAurora, Ohio, are one of the leading manufacturersof complete computer systems - from hobbyistright up to business and OEM applications.The single board construction and custom LSI

chips used in the Superboard II result in largecost savings, and ease of use. In fact it has morefeatures and better performance than some othersystems that are selling at up to £1,000. In the

- Standard Features

Uses the ultra powerful 6502 microprocessor 8K Microsoft BASIC -in -ROM

Full feature BASIC runs faster than currently availablepersonal computers and all 8080 -based business corn-putesr

4K static RAM on board expandable to 8KFull 53 -key keyboard with upper -lower case and userprogrammability

Kansas City standard audio cassette interface for highreliabilityFull machine code monitor and I / 0 utilities in ROMDirect access video display has 1K of dedicated memory(besides 4K user memory), features upper case, lower case,graphics and gaming charaCters for an effective screenresolution of up to 256 by 256 points, Normal TV's withoverscan display about 24 rows of 24 characters, withoutoverscan up to 30 x 30 characters

Extras Available expander board features 24K static RAM (additio-

nal mini -floppy interface, port adapter for printer and modemand OSI 48 line expansion interface

Assembler editor and extended machine code monitoravailable

early 70's computers with inferior performancecost over £10,000.The broad range of features include 8K BASIC

in ROM, up to 8K of RAM on board (4K supplied), full 53 key computer keyboard, Kansas Citycassette interface, video display interface (withgraphics). Available options include an expanderboard for additional 24K RAM, dual mini -floppyinterface port adaptor (for printer and modem).The Superboard II comes preassembled, and only

needs a power supply and case. Any 5V supply at3A will power it.

CommandsCONT LIST NEW NULL RUN

StatementsCLEAR DATA DEF DIM ENDGOTO GOSUB IF. GOTO IF THEN INPUTNEXT ON GOTO ON GOSUB POKE PRINTREM RESTORE RETURN STOP

ExpressionsOperators

/, t NOT, AND, OR.

FunctionsABS(X)LOG(X)SPC(I)

ATN(X)PEEK(I)SQR(X)

COS(X)POS(I)TAB(I)

FORLETREAD

. -RANGE 1037 to 10'"

EXP(()RND(X)TAN(X)

String FunctionsASC(XS) CHRS(I) FRE(XS) LEFTS(XS,I)

RIGHTS(X$ I) STRS(X)Plus variables, arrays and good editing facilities.

Fully built and tested. Requires only +5V at 3 amps and a videomonitor or TV and RF converter tobe up and running.There is enormous interest in Superboard II, so order early if you wish to avoid inevitably long delivery dates later thisyear.FREE 15 -DAY TRIALLotus Sound have had so many questions about various aspects of Superboard II that in order to save time, andensure your satisfaction. we are offering to return the full purchase price to anyone who returns their machine-ingood order and original packing-within 15 days of delivery.

LOTUS SOUND4 MORGAN ST., LONDON E3 5AB

Mail order only 01 - 981 3993 (24 hr answer)Callers by arrangement Telex 261426 Attn: Lotus Sound

22

FRE(X) INT(X)SGN(X) SIN(X)USR(I)

LEN(XS) MIDS(XS,I J)

VAL(XS)

Fro: LOTUS SOUND4 MORGAN ST., LONDON E3 5AB

Please send me Ohio Scientific SuperboardComputer(s)I enclose cheque / PO for £

Name

Address

CT1


Printout

Two word processingsystems from ComartCOMART has introduced twonew word processing systems,both for the Sol range ofmicrocomputers, which thecompany imports from theU.S.

Solstar runs on the Sol 20/16with mini -floppies. Correc-tions, additions, deletions andmovement of characters,words, phrases or blocks areaccomplished in a simple,direct manner, with all textcopy displayed on the memory -mapped video display for easeand speed of assimilation.

Wordwizzard runs on a Sol3 with 64K and a Helios dualdisc drive. Advanced facilitiesinclude the ability to print-outone text while editing a second,

Cromemco System 3

and a special keyboard tem-plate permitting operator com-mands to be implemented witha single key depression.

The So!star costs £2,500 andthe Wordwizzard £5,000, butboth need the addition of aprinter-the Diablo daisy-wheel is recommended-tocomplete the system. Both sys-tems have a four -week deliverytime.

The Sol microcomputerrange has several featureswhich have made it popular inword processing applicationsin the U.S.

It has a top-quality capaci-tive keyboard, ensuring reli-able keystroke performanceover a long period; the video

Latest Lib is for thecalculator userTHERE are genuine fears aboutmachines taking over every-thing, but it is still a shock tofind the machines apparentlystanding up for themselves.

Calculator Lib is, in fact,the title-probably meant toincrease the paranoia of themost neurotic of us-of thenewsletter of the LiberatedCalculator -users' Club. Set upby Canadian, Gene Hegedus,it is: "a truly universal, inde-pendent, non-profit group ofcalculator users (regardless ofthe make of the calculator)dedicated to exploring thelimits of the state-of-the-art ofcalculator -mathematics.

The overall goal is to profit

mutually from all members'knowledge of calculators andrelated fields, and create aforum which allows club mem-bers to meet and identify witheach other's interest. The clubneeds volunteer members toact as officers in the editorialcommittee, correspondents,reporters and translators.

Club members speak orwrite English, French, Germanand Hungarian. This list willhopefully be expanded withreaders in other countries".

For more information, sendlarge, self-addressed,stamped envelope to GeneHegedus, PO Box 2151,Oxnard, CA 93034.


display is flicker -free withoutthe "ripple -through" effect ofsome c.r.t.s ; and the equip-ment is designed stylishly to fitinto an office or home environ-ment.

The introduction of thesesystems, together with that ofCobol for Cromemco micro-computers, heralds the Comartentry into the commercial mar-ket; previously it has concen-trated on scientific, educationaland industrial applications.

The Cobol implementationis for Cromemco Z2 -D andSystem 3 microcomputers withat least 48K bytes of memory.It is written to AINSI 1974standard with all Level Onefeatures and the most usefulones of Level Two. It costs£85.

Also connected with themove into the business systemsmarket is the agreement withComputer Field Maintenanceto provide a nationwide fieldservice for the Cromemco,North Star, Processor Tech-nology, Dynabyte and Solmicrocomputer sytems Comartdistributes in the U.K.

There will be a standard 48 -hour or better response for anestimated cost of 12 percent ofComart list price for theproduct in question.

Service centres in Londonand Manchester will be fol-lowed by others in Glasgowand Nottingham.

Comart can be contacted fordetails of all its products andservices at PO Box 2, St Neots,Cambridgeshire.

Graffiti winneThis months winning entryis from Andrew White,aged 16, of 19 GreenparkDrive, Co Armagh, N. Ire-land.

The micro in the corner,Not used for o'er a week,Is moping for a program,Just waiting for a little

PEEK.

It's BASIC is getting hazy,Through a boring lack of use,Computers, too, have

feelings,And don't take kindly to

abuse.

But this eternal waiting,On a shelf for weeks on end,Is enough to drive a micro,To an enemy, from a friend.

Integral unitMICROCOMPUTER suppliersprobably have more new prod-ucts to launch than any othersection of the industry, so it isnot surprising that so manycapitalised on the Compecexhibition for initial exposure.

ISG Data Sales of Maiden-head premiered a new develop-ment system and terminal fromFuturedata Computer Corp ofLos Angeles. Advanced Micro-computer Development Sys-tem (AMDS) provides in oneunit a c.p.u., keyboard andc.r.t., claimed to be the firstsuch integral unit.

There is a choice of micro-processor c.p.u.-the 8080,8085, 8086, 6800, 6802 and Z80are offered; and a standard 64 -key keyboard and 12in. dis-play. Memory is expandablefrom 16-64K RAM.

A comprehensive set ofpackages is available for soft-ware development, includingdebug facilities, editors,assemblers and Basic com-pilers. There are also hardwarefacilities for debugging andemulation.

The 80 -character displaycomprises 24 lines of 7 x 9 dotmatrix with upper- and lower-case characters, enhancedvideo, reverse video, under-lining, highlighting and linegraphics.

A basic 16K system costs£8,000 from ISG Data Sales,Moorbridge House, 50-52Moorbridge Road, Maiden-head, Berkshire.

A customer enters,The micro he is shown,A demonstration "NOT

FOR ME"As 'cross the room the

customer is blown.

Take heed, you micro traders,Computers aren't just steel,Instead, inside that circuitry,Is something which can feel.

The runner-up is G. P.Dixon, of Windlesham.

Our micro has caught thedisease,

Of charging its users largefees,

It says-"Look here, GusI'm driving this bus,Sit down-log in-tickets

please".

23

`Most powerful' claimby IntelTHE iSBC 86/12 single -boardcomputer is the most powerfulmicrocomputer board to cometo the market so far, claimsits manufacturer, Intel.

It has a 5MHz CPU whichexceeds the PDP-11/34 inperformance and will replacefour standard minicomputerboards in a typical OEMsystem at about half the cost,the company says.

An 8MHz, soon to follow,will increase the gap in per-formance over mid -range miniseven more.

The iSBC 86/12 is a 16 -bitCPU, with memory up to 48Kbytes, dedicated parallel I/Oand serial communicationsinterface all on the same board.It plugs straight into thestandard Intel Multibus andcan be expanded using any ofthe wide range of expansioncards available from Intel orthe 100 other manufacturerswhich support the Multibus.

They include RAMS up to

64K bytes, ROMs, up to 64Kbytes, battery powered RAMboards, PROM programmerboards, mini and standard disccontrollers, hard disc con-trollers, 3M cartridge con-trollers, cassette controllers,video graphic boards, analogueI/O boards, keyboard/CRTcontroller boards, relay outputboards, isolated input boards,communication I/O boards,and communications con-trollers.

The arrival of the iSBC 86/12 reveals the purpose ofseveral lines on the Multibuswhich were not needed by 8 -bitminis. They are an additionaleight data lines and four moreaddress lines, increasing thenumber to 20 to cater for theone megabyte addressingcapacity; and a byte controlline, which allows both 8 -bitand 16 -bit CPUs to be usedon the same Multibus system.

Employing the 8086 16 -bitCPU, the 86/12 has a compre-

CCS MicrohireMICROCOMPUTERRENTALSPECIALISTS

Before you buy a micro, why nothire it for a day or a weekend?

From £2 a day we hire out a range ofmicros for evaluation/experience orprogram development.

Apple IICommodore Pet

* Nascom I or MicrosResearch Machines 380ZSWTC 6800 or MSI 6800Tandy TRS 80

Protect your future investment.Try out a system now.

For details write toCCS Microhire, Freepost,

Letchworth, Herts SG6 4YA

hensive instruction set whichincludes multiply and dividein binary, BCD of ASCII.

Communications arehandled by a separate V24(RS232C) serial port, whichwill support virtually any com-munications protocol. Baudrates for this port can be soft-ware -selected from 75-9,600in asynchronous mode, andfrom 1,760-38,400 in syn-chronous mode.

Other functions supportedare event counting, timing andvectored interrupts-the boardsupports nine, expandable to65, levels. The board also in-corporates an auxiliary powerbus and power failure interruptcontrol logic for employingbattery supply to protect thecontents of the read/writememory during a powerfailure.

Intel Corporation (U.K.)Ltd., 4 Between Towns Road,Cowley, Oxford OX4 3NB.

BristolboundTHE Nascom-1 microcomputersystem is now being distributedin the Bristol area by TargetElectronics, one of the largestsuppliers of semiconductorsand electronic components inthe area. The Nascom systemis the only microcomputer thecompany handles.

Target Electronics, is at 16Cherry Lane, Bristol BSI 3NG.

HarlowZ80 spotHARLOW -BASED distributorDistronic is offering off -the -shelf Z80 microprocessors fromMostek. It also has fulldevelopment facilities avail-able.

Full software support isprovided, with a strongemphasis on high-level lan-guages and a disc -baseddevelopment system offersadvanced real-time debugfacilities. The price for quantiesof 1-24 is £23.03.

Distronic, 50/51 Burnt Mill,Elizabeth Way, Harlow, Essex.

Kim 1 for lessthan £100COMMODORE has reduced theprice of its KIM 1 to £99.95p.

This price puts it well in therange of students, hobbyistsand schools, but it remainsideal for control applicationsand training in industry.

Commodore stresses thatthe Kim 1 is not a kit, but acomplete microcomputer witha fully -assembled PC board,needing only a power supply tooperate. Based on the MOS6502 microprocessor, it has2K bytes of ROM, 1K byteof RAM, a keyboard and six -digit LED display.

The system can be expandedsignificantly, starting with theKIM 3 8K RAM memoryboards (£193.32p. inc. vat).This can be wired in by theuser-all the required con-nectors are built-in-orattached more neatly by usinga KIM 4 motherboard (£96.12inc. vat).

An ordinary audio cassetteunit can be attached to provideauxiliary storage. All inter-

face circuits provided on theKIM 1 board including aTeletype interface, are readyfor connection. If the Teletypehas the facility, KIM can alsohandle paper tape input andoutput.

The range of peripherals foruse with the system has beenexpanded in collaboration withdistributors.

Options include a pocketterminal (£240), which allowsinput of the full ASCII charac-ter set from 40 dual-purposekeys; and a videoboard (£150)which allows a normal tele-vision to be attached as a videodisplay device.

Kim also boasts excellentdocumentation of hardwareand programming instructions,plus powerful software.

They include an Assembler/Disassembler/Editor package,an information retrievalsystem, a mailing list programfor business use, and a varietyof games. The prices of themrange upwards from £12.


Printout

Near -total paralysis has not prevented Chick Smith developing his interest incomputing.

100 timesfasterTURN your Pet into a smallbusiness system. That is whata firm in Solihull is suggestingnow that it has attached amini -floppy disc system to thePet.

Midland Micronics hasbolted two 51 in. floppy discsneatly on each side of theVDU. It is engineered veryneatly so that it looks part ofthe machine.

The advantage of usingfloppy discs is that it is muchfaster than a tape cassette andyou can hold more informa-tion. Midland says that eachdiskette can hold up to 81Kbytes of data and is 100 timesfaster to access than the tape.

Connection of the drives isvia the Pet memory expansionboard and the system is com-plete with an additional plugin PROM permitting controlof the disc system via Pet BasicUSR instruction with simplecommands from either the key-board or under program con-trol.

The floppy disc Pet is in twoversions, 24K or 32K, and thestarting price is £1,300. Morefrom Midland Mictronics,Oakfield House, Station Road,Dorridge, Solihull, W. Mids.

Micro interest viachess routeCHICK SMITH is a resident ofthe Thistle Foundation for theseverely handicapped in Edin-burgh. Near -total paralysishas not prevented him develop-ing his interest in computing.

An Apple II and cassetterecorder are mounted on atrolley beside his bed andoperated via a specially -designed separate keyboardmounted on a frame over thebed.

Chick operates the keyboardusing a perspex rod in hismouth. Control and shift keyshave been modified to lock inposition. His wife, Beth,changes cassettes when neces-sary.

A keen chess player, Chickfirst experienced the delights ofmicros after buying a ChessChallenger and rapidly dis-covering its limitations. He hasreceived help in installing theApple from staff of EdinburghUniversity and members of theScottish Amateur ComputerSociety, but is almost entirelyself-taught.

Programs he has writteninclude a number of gamesprograms and a chessboarddisplay. He also has the Apple

voice -response unit for whichhe is still developing applica-tions.

Paris inthe SpringLET Compec be a warning to allthose in the business of sellingor servicing small computers.Exhibitions are subject to thesame buoyant demand as therest of the industry.

In particular, those whocould not get space at Compecshould already be thinkingabout Europe Micro/Expo 79,which looks like being thebiggest in Europe.

Organised by Sybex Europe,it is scheduled for 15-17 Mayat the Centre International deParis and although the size ofthe exhibition hall has beendoubled, 20 percent of theavailable space had beenbooked before the first mailing.

An intensive campaign isalready underway using directmail, the technical press andTV-a 45 -minute special hasalready been screened inFrance-so the show is assuredof good attendances.

The majority of visitors will,no doubt, be from France butthe campaign is being takento all major European coun-tries, so there should be sub-stantial number of visitors.

More details can be obtainedfrom Sybex Europe, 313 RueLecourbe, F-75015, Paris.

Tiny Basic is hereTINY BASIC is not the managingdirector of a multinationaltrading empire but a newlanguage for the beginner tomicrocomputer programming.

Written by the Golden Rivercompany the language is de-signed specifically for a micro-computer with minimalmemory. It will accommodateapproximately 100 statementsin 2K bytes of Ram.

It includes all the basicfunctions of Basic, includinga line editor, an assortment oferror messages to the user anda surprising amount of pro-cessing capability.

Floating-point arithmetic,arrays, alphanumeric stringsand other advanced facilitiesmay be added via a machinelanguage extension.

The ability to expand thelanguage in this fashion makesit suitable for both novice andexperienced programmers.

It is supplied resident in a

2716 EPROM, or fusible linkPROM, ready to install in theGolden River Mk 4 micro-processor system or GRO430single board computer. It iscomplete with a manual andcosts, with chip, around £100.

Golden River is at TelfordRoad, Bicester, Oxon.

ChristmascompetitionNEXT MONTH we shall revealwho the nine lucky finalists arein our £5,000 Christmas com-puter competition.

By the closing date onDecember 31, our offices wereabsolutely swamped with en-tries with ideas galore for com-puter applications.

The nine finalists will thenbe asked to develop their deasinto a flowchart demonstratinghow the system could work.Don't miss next month's issueout February 15.


MICROCOMPUTERTRAININGMinicomputer and MicrocomputerSystems: Management Assessment

Microprocessors:Assessment and Application

Minicomputer and MicrocomputerSystems in Industrial Control andAutomation

Microcomputer Programming and DesignTechniques for Engineers

Microcomputers in Commercial DP

High Level Languages for Microprocessors

Microcomputer Techniques for ComputerSystems Designers

Advanced Microcomputer DesignTechniques

For further details of these Microcomputerthe form below.

5 March 19794 June 19791 September 197926 November 1979

6-8 February 19791-3 May 19794-6 September 197930 October -1 November 1979

21-23 March 197920-22 June 197917-19 October 19795-7 December 1979

19-21 February 197914-16 May 197917-19 September 197912-14 November 1979

1-2 March 197924-25 May 197927-28 September 197922-23 November 1979



28 February -2 March 197923-25 May 197926-28 September 197921-23 November 1979

training courses complete

Please send me information on Microcomputer training

Name

Job Title

Organisation

Address

Telephone Number

Return to:lnfotech International Limited, Nicholson House, Maidenhead,Berkshire. Telephone 0628 35031, Telex 847319.

26

Circle No. 133PRACTICAL COMPUTING Febraury 1979

Applications

Business packagesMany business packages are now coming onto the market. Thismonth we look at some systems available for estate agents andfor doctors.HB COMPUTERS in Kettering has devel-oped a package for estate agents for thePet. The total system at around £710-thesoftware selling for £15-was developedby HB with help from a local estate agent,Parkhouse and Partners.

It is a simple but effective way for estateagents to call broad details of a propertyon the screen while the potential customerdecides immediately whether moreinformation contained on filed broad-sheets is required.

Input is typed -in at the end of a dayfrom property detail sheets the agent com-pletes during the day as he views eachproperty. The main breakdown for eachproperty is price; the other kinds of inputdata include type and location, number ofrooms, number of bedrooms, garage,features, and so on.

When an enquiry on a property isreceived, the data tape of the appropriateprice range is read totally into memory-each data tape can hold about 60 prop-erties, depending on detail. As the cus-tomer decides his interest in eachproperty, the folio number of each broad-sheet in the files is noted and the pulledsheets are sent, or handed, to the potentialcustomer.

HB claims that about 30-60 minutes'training in the estate agent's office, givenby HB, is all that is needed to get the sys-tem started and running.

HB believes enhancements to the pack-age will provide automatic collation andmailing of property details to customers.It would also like to see an inexpensiveprinter attached to provide alternativeoutput.

Another estate agents' package is beingoffered by Compelec, of Berners Street,London, WI on its Series 1 system forabout £7,000, including the software.Bought over three years, it would costabout £60 per week. The package, similarto that used in the Altair 300 estate agents'

Computer Workshop-developing

system, is more comprehensive in its facil-ities than the HB package, as its priceindicates.

The Altair 300 is a multi-user systembut this is a single -user, single -office sys-tem using a 64K machine, 1 -megabytefloppy, a VDU and Qume printer. Someof its features include: Storage of up to 30,000 properties and

applicants; Ability to match properties with

applicants using up to 48 attributes; Applicant address labelling; Data analysis of stored items-e.g.,

number of properties notified,effectiveness of advertising, method ofapproach to the agent;

Immediate backlog listing-e.g., 50properties including price, address,office to contact, and brief descriptionof property can be produced in lessthan four minutes;

Automatic culling of applicants' listafter a pre-set review time;

Alphabetical listings available at anytime;

Modular system design means that afeature such as accounting or propertymanagement can be added later at areasonable cost.

For doctors, we have uncovered twoapplications for micros-the ComputerWorkshop MICKIE and the CompelecPatient Accounting System.

Computer Workshop of Dover Street,London, Wl, using software developed bythe National Physical Laboratories, prod-uced an application system for doctorscalled MICKIE-Medical InterviewingComputer.

To be used in five areas of DHSS tostart, the systems set up a patient/machineinterface where the patient answers ques-tions on the screen using a "button box"with only four buttons. Making certainthat the patient is first literate and canread the characters on the screen, the doc-

systems for doctors.

tor leaves the patient to complete thequestionnaire. The information obtainedis stored and then printed -out on theMICKIE printer in whatever format suitsthe doctor.

Patients apparently seem to prefer totalk to the machine because they can taketheir time answering questions. An inter-view takes about 40 minutes and its lengthdepends on the illness, the patient's age,and so on.

West Middlesex Hospital is operatingMICKIE for patients with abdominalpains and in the future will set upMICKIE for backache complaints. Doc-tors have praised the system because ofthe great savings in doctors' and nurses'time.

A different kind of doctors' package isbeing offered by Compelec, of BernersStreet, London, WI. The system, at about£6-7,000-the included software costsabout £1,000-is for account manage-ment.

The system generates a patient ledger,charges and receipts, new accounts, recallreminder list/labels, aged debt analysis,delinquent reports, practice income state-ments, and a query function.

Aimed at the single -site, single -usermarket, the system has at its heart theCompelec Series 1. The number ofaccounts and patients' data which can beheld is dependent on the length of therecord needed but the system shouldaccommodate the number of patientswithin a normal partnership easily-say1,000 patients.

Compelec expects to enhance the soft-ware to include insurance reports, treat-ment plan estimator, patient charts,appointment book, inventory control, andgeneral ledger.

Conclusions At the micro end of the market the

picture is relatively grim for usersseeking a very inexpensive system withthe application software already writ-ten, so praise for these items for at leasta start in the right direction.

There is a great opportunity for bright,innovative software houses to startattacking the industry application mar-ket. In the near future we will belooking at druggists' systems, solic-itors' packages, client accounting,temporary employment agency systems,management consultants' packages andperhaps publishers.

27

The popularity of Pet and the diversity of ideas from Petowners is to some extent acting as a focal point for micro-computer users in Practical Computing. So we are starting aPet Corner for those who have the Commodore baby-and forthose who wish they had.

These pages represent an independent collection of news andviews. The principal focus is Mike Lake, of the IndependentPet Users' Group (IPUG): if you wish to contact Pet Corner,write to him or send articles/snippets/ideas to us directly.

The idea of a group, completely independent of Commodore, was first conceived by Norman Fox ofWelwyn, Herts. He contacted several Pet owners and circulated a newsletter to everyone he knew.The group had its first meeting last October, when members met to discuss what the group could do.

Obviously the most important role forthe group is to facilitate communicationbetween Pet owners and users. All overthe country there must be users who arere -inventing the wheel over and overagain. If the group can provide a forumfor the circulation of information andideas, then it will have been a success.

At the second meeting of the group inNovember, James Chambers, of thepsychology department in London Uni-versity, allowed us to see some of the waysPets are used to help in experiments. Petsare the ideal method for teaching studentsprogramming, he said, and with theknowledge thus gained new ideas couldbe tried out.

We saw a Pet being used to operate avariety of experimental equipment; shut-ters, projectors, and stimulus -responsemeasuring apparatus. The day is with uswhen the experimenter can set up the Pet,let it control the experiment and thenproduce all the statistical results withoutdelay.

What IPUG offersWe hope that as well as regular

meetings, IPUG will be producing aregular newsletter for Pet users. Anyoneinterested should send £2.50 (payable tothe group) to the secretary, Mike Lake, at9 Littleover Lane, Derby.

Thanks to the help of Julian Allason ofPetsoft we have been able to circulatemost Pet owners with information aboutthe group. You don't have to be a Petowner to join. though-just contact Mike.

Hardware : Mike's moansWhy is it that so many items we may

wish to interface with Pet are so ex-pensive? To take one or two examples:a TV interface has been offered by one ortwo companies at £75. My prototypewhich, incidentally, works well, cost lessthan £5. Even with all the connectors andswitches I put on the final version, it costonly £10. Someone, somewhere is tryingto rip us off.

Secondly, what about additionalmemory? Anyone who has compared thecosts of commodore memory for Pet with

the prices for the Tandy TRS-80 must befeeling sick. I know all about the problemsof importing American boards but withan expanding market here, isn't it timesomeone made a good British -madeboard at a reasonaLle price ?

Practical Computing will be havingPlessey's Petite add-on memory for ahands-on test in the next few weeks;watch this space.

Connectors to the outside world fromthe Pet ports are still hard to obtain.Some are supplied without a cover. Notonly is this not aesthetic, it could alsocreate shorting problems. If suppliers ofdecent connectors will contact us we willprint a list.

Now a moan at Commodore. Thecassette unit has two irritating problems-it may sometimes partially erase the tapesused for writing on, and head alignmenton different machines may be so far outthat tapes produced on one Pet cannot beread on another.

These are not major defects to solveand it seems a pity that, after producingsuch a good machine, Commodore hasnot been a little more forthcoming onthese issues.

A minor but equally irritating pointwhich has been bothering a number ofowners is keytop wear. If your Pet is usedregularly, in a few months it will becomeimpossible to read some of the keys-particularly RETURN and SHIFT. Thisis because the key label is only stuck on;a well -designed machine then becomestatty through a relatively trivial problem.

We will print any decent solutions.Please send your suggestions quickly-Mike's keys are just beginning to giveproblems.

Simply softwareOn the subject of PEEK and POKE,

try this in the middle of a program:WAIT 59410,4,4

When everything goes dead, try pressingSTOP. Surprise, surprise-nothing hap-pens. To put yourself out of your misery,.press SPACE. All should then be well.This could be a very useful device forpreventing anyone stopping an important

program in mid-flight. Perhaps you maybe bold enough to try:

WAIT 59410,1,1 and WAIT 59410,2,2 andWAIT 59410,8,8 and WAIT 59410,16,16. I don'trecommend WAIT 59410,32,32.

Here is another nice one:

POKE 59409,52

This will make the screen go dead. Nowtry:

POKE 59409,60

and all should reappear.This is very effective in a program if you

set up a screen of information with thescreen POKED out, then POKE it inagain. An instant screenful will appear.

Music to our earsPet is not an excellent musician but it

can play tunes. If you want it to startplaying notes then it is very easy. First,connect up the user port like this:

User Grid <-Port (Pin N) 470K

150 To amplifier

CB2 <(Pin M)

The output can go to a hi-fi or to asimple amplifier feeding headphones(Circuit next month if enough peoplewant one).Now the magic pokes:

POKE 59467,16POKE 59466,15 (or 51 or 85 try them all)POKE 59464, any number 1-255

You should now hear a tone from thespeaker. You can control the length of anote by the use of a loop, or by checkingthe timer. I will give a full list of notes,frequencies and poke codes next month.You MUST POKE 59467,0 after use oryour cassette will not work.

Book bickerA good deal of reading matter is

available for those setting out with Basic,but what about those who wish to take upmachine language programming on thePet? The 6502 software manual is fine,but is written at a fairly advanced level.

(continued on next page)


Pet corner

(continued from previous page)

Independent informationThere are four good independent U.S. newsletters for Pet:The Pet Gazette, Cursor The Pet Paper, Pet Users' Notes,Microcomputer Resource Centre, P.O. Box 550, P.O. Box 43, P.O. Box 371,1929 Northport Drive, Goleta, Audubon, Montgomeryville,Room 6, California 93017, Pa 19407, Pa 18936,Madison Wi 53704 U.S.A. U.S.A. U.S.A.U.S.A. (Monthly) ($2 per copy, monthly) ($10 for six issues per year)(Free, monthly)

Is your memory good?A VITAL component of your processor isthe memory. A single faulty bit in a 32kilobyte system represents an error of onlyabout 0.000381 per cent but can createchaos with your programs, giving com-plete program failure or, possibly worse,still inaccurate results.

Though the bits which make up eachbyte are often used in terms of "leastsignificant", "most significant", and thelike, a faulty memory cell is just asdestructive to performance, whicheverbit it represents. Fortunately, because ofthe nature of a processor, it is notnecessary to resort to the use of oscillo-scopes and logic probes to check eachstate of every cell; a suitable softwareroutine will enable the system to checkitself.

Test programsThe author first decided on producing

a test program for his MK14, SC/MPII-based microprocessor unit and has sincegenerated a number of variations. Re-produced here are the original simple -approach listing for the SCMP and a moresophisticated version written in Pet Basicwhich is readily adapatable to othersystems.

Both programs are based on the premisethat it is necessary to test that all bits inall locations can be set to retain a logicalone or a logical zero. The approachchosen is first to write 01010101 (i.e.Hex. 55; Dec. 85) check the location(s),then write 10101010 (i.e. HexAA ; Dec170) and again check the contents.

In the majority of cases this willproduce an accurate indication of thequality of memory and enable faultconditions to be interpreted readily by

examination of the value of the contentsreturned at the two checks.

If it is suspected that certain patterns ofdata are causing peculiarities, either pro-gram could be adapted readily to checkthis. In addition in certain cases, e.g.when using dynamic memory, it may benecessary to insert a delay between thewrite and read operations to allow a"leaky cell" to be detected.

SCMP is the first version with noattempt at auto checking. All memory

by W D Mercer

locations specified in the program areloaded with Hex. 55; these locations arethen checked visually on the MK14

manually steppingthrough memory. The program is re -runto load Hex.AA to all locations and thecontents checked as before.

As shown, the listing is for the standardmemory supplied with the MK14; theoptional RAM may be checked by chang-ing OF13 to OB; OF16 to 00; andOF24 to 00.

The Basic Pet listing given is for a fairlysimple but nonetheless informative ap-proach. The program could be expanded,e.g. to include Hex. as well as decimalreadout of the location of faulty cells, oreven to analyse the fault return toindicate which bits of the word are inerror. All, however, entail a longer pro-gram; since the locations used for theprogram itself cannot all be checkedbecause of the use of the POKE command,it is desirable to make the program asshort as possible.

The locations used for the program

Listing for SCMPOF12 C4OF LDI Start Loc. Hi.OFI4 35 XPAH 1

OF I 5 C4213 LDI Start Loc. Lo.OFI7 31 XPAL 1

OFI8 0455 LDI (55) LOOP STARTOFIA CDOI ST (a 1(1)OFIC 31 XPAL I

Of 10 C80C ST POINTOF I F 31 XPAL I

OF20 C009 LD POINTOF22 02 CCLOF23 F407 ADI 7OF25 9CF1 JNZ -15 ANOTHER LOOPOF27 3f XPPC 3 RETURN TO MONITOROF2A POINT

For second run change OFI9 to AA.

can then be checked manually from aprogram listing. As indicated the lowest"start address" must be above the highestlocation used by the program; on Pet thismay be found by use of the FRE(0)function, remembering to allow space forthe storage of the program variables.

Note that as given the program restoresthe original information to the memoryafter checking; this allows for thisprogram to be used as a subroutine,checking locations which contain programor data information. If desired, this,together with the various "presentation"prints, may be omitted, resulting in ashorter and faster program. As given theprogram takes about one minute to checkone kilobyte of memory.

Running the programAs indicated, execution may be speeded

by deleting lines 25 and 30 and the POKEstatement of line 100. The FOR . . NEXTloops in lines 40 and 70 act as delays ofabout 10 milliseconds as described in thetext.

On a standard 8K Pet the followingwas obtained (initially? 8191-FRE(0)gave 129o, allowance for variables soSTART =1350)RUN

MEMCHEK 02, WDMOCT78START ADDRESS? 1350END ADDRESS ? 8191@2048@3072@4096@5120@6144

@7168READY

?8 19 I-FRE(0) gave 1332, hence minimum safe startaddress is 1336. This Pet had four faulty cells in the onememory section. Three had problems in BITO, one inBIT2.

44267> 85 < 84*6331> 170 < 171*6400> 170< 174tf 6461 > 170< 171

Listing for PET5 PRINT"clr"TAB(10)"MEMCHEK*02, WDMOCT78"

10 1NPUT"START ADDRESS";A:INPUT"END ADDRESS ";B20 FORI =ATOB25 1F1/1024 = INT(I/1024)THENPRINT"@"130 X-- PEEK(1)40 POKEI,I70:FORJ=IT010:NEXT:T=PEEK(I)50 IFT=170THEN7060 PRINTTAB(8)"#"1">170<"T70 POKE1,85:FORJ=IT010:NEXT:T=PEEK(1)80 IFT.---85THEN10090 PRINTTAB(8)"*"I">85<"T

100 POKEI,X:NEXT


Keen Computer5,go SOFT!

A full range of Lipple II software is now being developed:

5oFtware available at present:

Incomplete record accounting £250 Shape -Create £ 25Addressing Et Mailing program £ 50 Co -Resident Assembler £ 25Word -processor £ 50 Matrix Inversion £ 25Information retrieval system £ 50 Full range of statistics packagesChequebook £ 10 available from £ 35

In addition to these packages, we also offer a consultancy service.

I rdcoareMean Computer5 are the only cippla II dealer in the Midlands area.The APPLE II has to be the most advanced Micro on the U.K. market.- It uses a 6502 microprocessor-a very updated version of the Motorola 6800.- It has excellent colour graphics and a very comprehensive basic.Apple II computer (16k) £985 Disk unit without controller £375Additional memory £200 Applesoft ROM card £115Disk unit with controller £425 Printer card £110

Ijeen Computer5 are now distributors of the new attachemicro -computer.- 16K RAM-IBM format dual disks-from £1466.Full range of printers available.

For further information please contact:

Haan Computer) Ltd,5 The poultry (off Market Sq)

nottinghamTele: nottm

50.1254/5/6Circle No. 134


30

Review

Construction never lessthan excellentTHE CROMEMCO manufacturing companynow makes a range of computers andboards using the Zilog Z-80 and the S-100 bus. A typical system with two mini -floppies and 32K bytes plus serial andparallel outputs will cost around £2,500.You can buy the 21 -slot motherboard boxcontaining the processor and a minimalamount of memory for £600. What youwill be able to do with it is anothermatter.

The Cromemco equipment is more thanjust another S-100 micro box. There is awhole range of interesting boards andexcellent software for the system. In thiscountry the equipment is imported byComart and distributed through agrowing range of computer shops.Comart also makes MicroBox-an S-100card frame (and a British S-100 productat last), which enables you to purchasea single -disc system for just over £1,000.

The Cromemco Z -2D is the top -of -the -range system with mini -floppies. A prac-tical system to use the software efficientlywould require 32KB memory. The proces-sor and disc controller each occupy oneslot of the S-100 box and there is a serialoutput as well on the disc controller,which means you can interface most ter-minals to your system immediately.Because of the way the software is con-figured, however, a second serial outputprobably is desirable if you want hard -copy output.

First, the good points. The standard of

design and construction of the boards isnever less than excellent. They are double- sided, solid and well -made.

The manuals from Cromemco are alsovery well-produced-Cromemco uses itsown word processing software-andwould put many minicomputer companiesto shame. The quality of documentationin the microworld is often little short ofdisgraceful, so this is no small achieve-ment.

The single worst point about theCromemco Z -2D is also immediatelyapparent. The mechanical design of theframe has been structured to make it easy

by Richard Stevensto construct but it is inadequate for prac-tical use. Immediate modifications arerequired to put the front panel on hingesfor easy board access. A front panel re -setbutton and on/off switch are also verynecessary.

The processing chip is based around thefamiliar Z -80A, normally operating at4MHz but with a switch to operate at2MHz for slower memories. It is alsoswitch -selected to jump at switch -on toany 4KB boundary. The board is also tot-ally compatible both in hardware andsoftware terms with the Altair and Imsaicards, the Adam and Eve of S-100 sys-tems.

The memory boards Cromemco sup-plies are not competitive for price with

those from the specialist manufacturers'and so Comart normally will supply thesystem with the Dynabyte 16 or 32KBboards.

By any standards, and especially bythose of the micro business, the 32Kboard has proved very reliable, despite thefact that it gets very very hot during nor-mal operation. It is not possible to movethe 32K board in memory very flexibly.While one board is a good basis for a sys-tem, care therefore should be taken aboutsystems which require PROMs at partic-ular positions in memory.

The Z-80 can address only 64K bytesof memory but the Cromemco processorhas the ability to select one of eight pagesof 64KB of memory. The 32K board isnot configured to operate in this way butthe 16K memory is-and it can also puteach 4K block of memory at any point inthe 64K memory area.

The semiconductor memory can bewrite -protected, set so it is possible onlyto read the contents and not to write intoit-it sounds a buzzer if you try.

So, all in all, the 16KB board is muchmore flexible, even though it occupiestwice as many slots. These points may beacademic for a system which it is tooperate untouched on a shelf but they arevital considerations if you expect to bealtering or improving your system in thefuture-and who doesn't?

The UK agent, Comart, is reported to(continued on next page)



be generally reliable and helpful-apleasant change. In the last few monthsthe company has apparently been so over-worked that the original level of good andrapid service has slipped a little, as itwould admit itself. This seems to be oneof the inevitable growing pains in themicro world and we would certainly notwant to criticise Comart seriously becauseit has been significantly better than mostmicro firms with which our reviewer hasdealt.

Discs and Discoperating systems

The Cromemco Z2-D uses two Wangcomini -floppies costing around £1,400 witha disc controller. They are rather slowerthan the North Star discs Comart sup-plied formerly but they seem to be veryreliable.

The Wangco discs are file -orientatedrather than memory -orientated, whichwas the case with North Star. The Crom-emco software is linked to the Wangcodisc and is now much better at disc hand-ling than the North Star version. It wouldno longer be sensible to choose North Stardiscs.

Each diskette holds 81K bytes accessedthrough CDOS-Cromemco Disc Oper-ating System-. A system with one disc isnot a really happy proposition unless fin-ance, or lack of it, leaves you no alter-native. The disc controller can handlethree mini -floppies and has a serial andparallel port as well.

One particularly aggravating omissionin the operating system is that there is nocommand for the complete copying of adisc from one system to another. On theother hand there is no specific "squeeze"command to compress the information onthe disc to leave room for a large file; sur-prisingly, this happens entirely auto-matically.

CDOS has some sophisticated com-mands apart from the standard range youwould expect. For example, the "batch"command enables the construction of a

series of CDOS programming steps whichwill then operate in an unattended mode-very useful for repetitive clockingthrough of a series of commands.

There is also a more simple monitorcalled RDOS-Resident Operating Sys-tem. It operates as a primitive operatingsystem for those unhappy souls con-demned to work without a disc.

Disc controllerThe disc controller is a single S-100

card able to control any combination ofup to three mini -floppies and four full-sized floppy disc drives. It contains abootstrap PROM to enable CDOS to beextracted from the floppy disc auto-matically on power -up. Also on the boardis a serial port for RS -232 or 20mA con-nection-and how is it all crammed on?

Single -board computerThe single board computer is an inter-

esting card which, with the addition of apower supply, can act as a self-containedcomputer. The big advantage of this isthat it is entirely S-100 compatible. Thewhole program can be developed on theS-100 bus and then transferred intoPROM, to produce a fairly cheap stand-alone system for process control applica-tions. The single -board computer can betested inside the Z-2 box before beingmoved.

At present the board is expensive at£345, presumably the level the market willaccept but it is certain to fall in price.Cromemco control Basic and a programcan be stored in two ultra -violet erasiblePROMs-which, of course, can be pro-grammed directly from the working pro-gram. With programming becoming moreand more expensive and memorybecoming cheaper, this combination is asensible approach to system design forsystems where only a few boards arerequired.

The board contains: Z -80A processor chip. RS -232 serial input/output. parallel data port.

room for PROMs. five programmable timers.

TUARTThis lovely acronym references the

Twin Universal Asynchronous Receiver/Transmitter-the standard Cromemcoboard for inputting to and outputtingdata from the Z-80 processor. A terminal,Teletype or line printer normally wouldoccupy one of the four input/output ports.

The board is packed with functions-asingle 10 in. by 5 in. card contains twoserial ports (RS -232C or 20mA) and twoparallel outputs with 10 software -pro-grammable timers, all for £185.

The baud rate is programmable from110 to 76,500, a really useful featurewhich prevents you having to grope in thecomputer's innards to alter tiny switches.

There have been some reliability prob-lems, however, with the TUART. This isstrange because it seems well -constructed,even if rather full of components. DavidBroad of Comart told us that we had beenunlucky and that there is no serious prob-lem with the board. Indeed, the Crom-emco equipment was voted the mostreliable in a poll of U.S. computer shopslast year.

It may seem like gilding the lily but ingeneral it is our impression that theTUART could be improved significantly.If the board could store a buffer of, say,128 characters while the processor isworking, the programmer could type -inseveral lines of code which could runwhen the computer had finished accessinga disc. The mini -floppies used in the sys-tem are relatively slow and the operatingsystem is configurated so that the pro -



32

Review


grammer is often kept waiting for five to10 seconds before something can be typedin mechanically; this time could better bespent thinking constructively.

Despite this niggling criticism, though,this board is a marvel of technology anda real bargain.

Parallel boardThis board is not one we have had occa-

sion to use. It is for the analysis of digitaldata and contains eight 8 -bit parallel portsfor taking data into and out of the S-100equipment. A useful little feature is anisolated input-output pair, with opto-isolated protection on the input and relay -protected output isolation-just right forelectrocuting the mother-in-law by com-puter.

An essential pre -condition for buyingone of these boards is an understandingfriend with a flat -cable former. This is areally useful device for making a largenumber of connections to flat computercable in one simple operation-ourreviewer's soldering is so slow that itrepresents a 5,000 per cent productivityincrease for making a 25 -way socket.

SoftwareThe Cromemco software is becoming a

very powerful collection indeed. There isFortran; a very good semi -compilingBasic; a small Basic which needs only 3Kbytes; word processing-the vendor is alittle coy about this and prefers to call it"text formatting". On the horizon areCobol, Pascal and database managementsoftware.

None is at all sub -standard, even bycomparison with their minicomputerbrethren, and the manuals produced forthem are excellent. Practical problems,however, are reported when runningFortran with the mini -floppies and only162K bytes of total storage.

Semi -compilingextended Basic

Basic was defined originally to be aninterpretative language-that is, when theprogram is run, the original program isinterpreted line by line. This makes the

programming easier but the processingtime much slower than a compiler lan-guage like Fortran, where the program isreduced normally to machine code by a"compiler" before it runs. Even theslightest alteration in the Fortran pro-gram means that the whole must bere -compiled, a tedious process.

The 16K extended Basic is semi -compiling. This means that after everycarriage return the program line entered ischecked for syntax; each syntactic mis-take is thus corrected by the programmerwhile the program line is fresh in themind. The line is also interpreted at thattime and placed into memory. This savesthe same line being interpreted every timethe program goes round a loop.

This makes for a very good compromisebetween a compiling and an interpretativelanguage. Little of the flexibility of Basicis lost, yet the processing time is decreasedsignificantly.

This version of Basic is very compre-hensive and takes about 14KB for theinterpreter, so to run a sensible systemrequires about 32Kbytes of RAM intotal.

Among the features are extensive for-matting capabilities (including the PRINTUSING command); 14 -digit precision,with the ability to reduce this if speed ispreferred to accuracy; integer storage-very useful for storing large arrays; dyn-amic error trapping, which allows theprinting of a pre -defined message on anerror condition; easy interfacing toassembly language programs; and sen-sible disc input/output facilities. A full listof the Basic functions is included in thespecification with this review.

Control BasicThis software is a "mini" version of

Basic, useful for those with small bankbalances and memory, but intendedmainly for implementing small programsvery quickly on single -board computers.Despite the fact that it occupies a mere3KB it contains a good selection of Basicfunctions, albeit in a stylised form.

Presumably Cromemco introducedinvestment in the form of programs in thelanguage. This version conforms in full to

the American National Standard Versionof 1966 and so should be more or lesscompatible with any programs runningon older machines.

If you intend running Fortran pro-grams, the full-sized floppies, with 250KBcapacity, are probably a better bet thanthe mini -diskettes; Fortran always seemsto finish by taking an enormous amountof disc space for one thing and another.

The compiling speed is several hundredstatements per minute, surprisingly fastreally. The Fortran program is composedusing the Cromemco Text Editor, a pro-gram whose commands bear similaritiesto TECO, the de facto standard used byDigital Equipment; in one or two pointsthe Cromemco editor is superior. Editorsare used so intensively by programmersthat it would be highly desirable to stan-dardise on one set of shorthand com-mands for all editing systems. The sameediting system is used for entering text forthe text formatting software.

Macro assemblerCromemco really went to town over

this system for writing Assembly languageprograms and it is as good as any microassembly software.

For a start, it is re-locatable-a veryuseful feature and difficult to implementbecause of the nature of today's micro-processors-both Intel and Zilog havelearned the lesson for their new 16 -bitmachines.

A macro is a little set of assembly levelinstructions which can be grouped intoone self-made instruction, which can thenbe used on its own. A library of commonmacros can then be formed and used.Macros have much in common with sub-routines but they may have significantlydifferent effects in use.

The debugger, another chunk of soft-ware associated with this package,enables the disassembly of any programinto the mnemonics of assembler lan-guage. Of course, neither the labels usedby the original programmer nor the pro-grammer's comments are available butdisassembly is an extremely useful tool.

The contents of memory may be altered(continued on page 35)

Technical SpecificationsDimensions: 19 in. rack -size width x 13 in. high x21 in. deep.Weight: about 501b. depending on configuration.Memory: expandable to 64 Kbytes.VDU: Any, conforming to RS -232 or 20mA loop con-ventions - e.g. Lear -Siegler, Lyme, Newbury, and thelike.Storage: Mini -floppies with 81 kbytes per diskette;8 in. floppies with 256 kbytesidiskette.

Operating Systems:RDOS: simple commands to examine, change, or movememory. Primitive disc -copying facilities.CDOS: Cromemco Disc Operating System; good file -oriented operating system used for initialising discs oftransferring files.

Languages:FORTRAN: to ANSI 1966 standard.SEMI -COMPILING EXTENDED BASIC: compre-hensive set of commands, good file -handling functions:LET REM INPUT READ DATA RESTORE PRINT PRINTUSING SPC TAB FOR -NEXT IF -THEN GOTO GOSUB

ON ... GOSUB DIM STOP END PEEK POKE SYS DEFFN USR INP OUT ON ERROR LIST RUN DELETEAUTOL RENUMBER CON SCR SAVE LOAD ENTERCREATE ERASE TRACEINC'TRACE ECHO/NOECHOESC/NOESC/ON ESC SIN COS ATN TAN RADDEG ABS EXP FRA FRB INT IRN LOG MAX MINRANDOMISE RND SGN SQR ASC CHRS LEN POSSTRS VAL OPEN CLOSE PUT GET PRINTINPUT-IOSTATCONTROL BASIC: mini (3Kbyte) version, ideal forstoring on PROM with a reasonable selection of com-mands.Functions: CALL PRINT LOCK LOC NEXT AND LETSTEP TO GOSUB REMARK SGN EPROM PUT OR NEWNULL GET LIST STOP WIDTH IF RUN XOR FORQUIT RND OUT IN LOAD ABS INPUT SAVE GOTORETURN SIZEEDITOR: Used for creating FORTRAN and TEXTFORMATTING files.MACRO ASSEMBLER: comprehensive package (in-cluding TRACE and DEBUG) for writing and debuggingassembly language programs.TEXT FORMATTING: Good package for handlingtext for reports. All standard facilities, including abilityto leave space for diagrams, page headings and num-bering.

U.K. DealersComputabits Ltd, 41 Vincent Street, Yeovil, Somerset(0935) 26522.Newbear Computing Store, 7 Bone Lane, Newbury,Berkshire RGI4 5SH (0635) 46898.The Byte Shop Ltd, 426-428 Cranbrook Road, Ilford,Essex IG2 6HVV (01) 554-2177.Xitan Systems, 31 El phinstone Road, Highcliffe, DorsetBH23 5LL (04252) 77126.Computer Workshop (Manchester) Ltd, 29 HangingDitch, Manchester (061) 832 2269.Comart, PO Box 2, St. Neots, Huntingdon, Cambridge-shire PEI9 4NY (0480) 215005.

PricesTypical system configuration:Z2 -D Software Development System: Chassis, powersupply motherboard, CPU card, six sockets and fan,L575.Disc: controller and disc, £845.32 Kbyte RAM, L695.Either FORTRAN, MACRO, BASIC, C85; Total price(Assembled), L2,205.


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Circle No. 135

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Circle No. 136

34

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(continued from page 33)

in real time by typing in assembly langu-age. Trace facilities enable the pro-grammer to move slowly through theprogram at the machine instruction level.Break-points can be set to occur atsuspicious points and the registers andmemory examined.

Text formatingCromemco avoids the use of the term

"word processing" because this softwareis not meant for people unfamiliar withthe text editor. A day or two would berequired to familiarise yourself with thispackage but afterwards it will remove allthe drudgery from report writing, especial-ly if you are one of those people whoalways seem to need give one more correc-tion to any piece of text. Right-handmargin justification, automatic pagenumbering, stopping the typewriter aftereach sheet has been processed, text indouble columns-it all seems to be there.

A point worth noting is that the wordprocessing software is written to takeadvantage of the Cromemco line printer,a parallel input device with great flexi-bility and high -quality daisywheel output.It can do things like underlining and over-printing, and it even adjusts the words in ajustified line so that the spaces betweenthem look exactly equal. This is notpossible with a normal terminal, which

not have the ability to move afraction of the space of a letter.

Such printers are few and far between-most people will be lucky to have accessto a cheap serial printer. To get these towork requires a slight modification toCDOS-details soon.

Control of the printer is, of course,automatic in the text formatting systembut a hard copy of the VDU output canbe obtained by pressing Control P at anytime.

Other boardsCromemco makes a series of boards

which illustrate the flexibility of the S -I00bus. If you buy S-100 equipment, youhave access to the products of dozens ofmanufacturers, all in cut-throat competi-tion with each other; despite this, one ortwo Cromemco boards have becomenear -standards.

If you want to take in signals from thereal world, do something with them, andthen tell the world what to do, the A -Dboard is the thing for you. There areseven analogue channels with seven foroutput, and a digital input and outputas well. And it is usable from Basic aswell. The analogue channel is sampled toeight bits and appears as a value between0 and 255 with a simple INP command;similarly, an eight -bit value can be sentto an output port with an OUT command.

What you do in between is up to you.Even by minicomputer standards, thisboard is no sluggard; it has a five -

microsecond conversion time, whichcompares well to the minicomputerequivalents. For process control of equip-ment this board is absolutely ideal.

The Bytesaver board is one of thosewell-known Cromemco offerings. It is forprogramming and using programmableread-only memories and is based aroundthe industry -standard Intel 2708/2716chips. Once the chips are programmedthey retain their data almost indefinitely,until exposed to a powerful ultra -violetlight. The board is very easy to use andsoftware commands which transfer datafrom RAM to the PROM are built intothe operating system software. Theoriginal Bytesaver-still available-holds8KB; the new version will hold up to16 of the 2KB 2716s, if you can affordthem.

The Dazzler is a pair of boards nowmore than three years old, a veteran byS-100 standards. Essentially it is an inter-face to a colour TV enabling the genera-tion of 64 x 64 resolution colour pictures.Unfortunately, it was designed for Ameri-can TV standards, though it will work-after a fashion-on British equipment.

It is probably not worth consideringnow Cromemco is certain to produce abetter version in the near future and inany case for the present there are betterS-100 graphics boards on the market. Thepoor resolution is a hindrance to anydelicate work but some spectacular pro-grams, such as a dramatic ever-changingkaleidoscope, have been generated.

Cromemco System 3The de -luxe end of the range is the

Cromemco System 3, a posh version ofthe Z -2D. Not only is its paint job muchbetter, it has full-size floppies (up to four)and its beautiful mechanical constructionmakes its cheaper brethren look badlydressed. The S-100 bus slides out on a neatrack for easy access. The software isabsolutely identical to the Z -2D.

The price of this system, at around£4,000, is approaching that of a similar16 -bit micro like an LS1-11 configuration.Discussions on the relative merits of thetwo systems is outside the scope of thisarticle but in passing it is worth pointingout that the LS1-11 probably has thesuperior operating system-after all, it hashad longer to evolve.

A budget version of the CromemcoSystem 3 would be the Z-2 with someexternal floppy disc system giving full-sized floppies at some discount.Coming soon-

A logical addition to the Cromemcorange would be a rigid disc, a cartridgeable to store something like 20-40megabytes. This is essential for any

large-scale record storage-mailing lists,for example, or writing the Great EnglishNovel with your text formatter. Re-member to keep back-up copies-it wouldbe awful to wipe it all out on page 887.

A much better graphics display optionshould also be on the way: this is themain weakness of Cromemco comparedto some other equipment, especially theApple II, of course. Hopefully, Cromemcowill remember the UK television stan-dards at the design stage: if not, theremight be another golden opportunity fora British manufacturer to miss.

Conclusions Cromemco has assembled a fairly

powerful system with very good soft-

ware and a fine operating system-much more important than any differ-

ences in hardware.

Not the least of its advantages is theflexibility of buying an S-100 kit,

giving you access to the equipment

supplied by more than 100 other manu-

facturers of hardware, boards and soft-

ware.

No one firm can charge you too much

for any single piece of equipment, at

least not for too long. If anyone should

sneer at slight incompatibilities between

some S-100 equipment, ask them to

name equipment for their system you

cannot get for the S-100 bus.

The Cromemco kit is bulky, with 21S-100 slots available. No power -supply

problems are likely because of the con-

servative design of the equipment. The

well -developed and well -presented soft-

ware will make it a tempting proposi-

tion even if the size of the equipment is

something of a deterrent.

For someone who would be contentwith a smaller, neater, cheaper system

with fewer slots, there are many

alternative S-100 systems on the

market which might make for a

reasonable comparison.


OHIO SCIENTIFICThe State of the Art in Small Computers.

Following the successful launching at Compec,we are pleased to announce that the full range ofOHIO SCIENTIFIC machines is now available,with good delivery. Example systems are: (TheC2 4P with mini -floppy, 20K RAM, and personal,games, business and educational discs; andC3 OEM with twin standard floppies, 32K RAM,and a range of optional languages.

C2 4P-MF-£1,595C3 OEM £2,950

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DEALER ENQUIRIES WELCOME

Circle No.

N%..0,

0,".> Commodore - Tei

Ohio Scientific - CompucolorThe following is a selection from our large stockPET SERIESPet 2001 8K £643.522nd Cassette £55.00Unidirectional InterfaceI-EEE to RS232 £99.50Bidirectional Interface £175.00DAMS Joystick (with

software) £25.00DAMS Page Printer Interface

(to 20m.a. loop) £25.00DAMS 625 Video Adaptor £25.00(complete for TV or Monitor)

All prices exclude VAT.

APPLE 16K £985.00Apple Disc £425.00

COMPUCOLOR 2 £1331.938K, Colour VDU, with 80K disc

OHIO SCIENTIFICSuperboard 2 £296.00500 Board £285.00

KIM 1 £99.95Kim 3B (8K exten) £129.95Kim 4 (Motherborad) £69.95

We stock Manuals, Documentation, all CBM & Petsoftsoftware. DAMS software includes specialist scientific,mathematics routines and games for Pet all at £4.00 +VAT. Send S.A.E. for comprehensive catalogue.

TEI-Professional Systems8080 based, CP/M, Mixed disc drives, Cobol, Basic,

Fortran 4, Pascal. Standard and Personalised packages forStock Control, Accounts payable, Accounts Receivable,Word Processing etc, for the commercial user.

Please ring Graham Knott or Jeff Orr for details ordemonstration.

DAMS (Office Equipment) Ltd.30-36 Dale Street, Liverpool, L2 5SF

Sales 051-227 3301 (10 lines)

Circle No. 139

STAN SYSTEMSouthern England stockists for CROMEMCO

Selected nationwide by Government departments,Research Establishments, Universities, Profes-sional Consultants, Assurance Companies, In-dustry and the serious hobbyist. Features includea range of software equalled by no other manu-facturer for price and performance. Fortran,Basic, Cobol, Z-80 Macro Assembler, Trace, andWord Processing, all at only £85 each. XitanSystems can supply CP/M for use on Cromemcoequipment with 8 in. floppy discs.

THE machine for professional use

>VAN SYSTEM, 23 CUMBERLAND PLACE, SOUTHAMPTON SO1 2BB. TEL: (0703) 38740

Also suppliers of: PET * HORIZON * PT SOL * DYNABYTE MEMORY * BOOKS * VDUs * PRINTERS

36 Circle No. 140


Software

Payroll and the PetWORKING -OUT the payroll is one of themostboring chores of any business. With thecomplexities of calculating PAYE andNational Insurance, most organisationsare only too willing to leave it to a book-keeper or accountant.

It is these repetitive calculations, how-ever, together with the need to store data,which makes it an ideal application for acomputer.

Many of the letters to our Feedbackcolumns have asked how payroll couldbe handled cheaply. To be honest, to buya computer just to work out payroll forfewer than 10 employees is hard to justify.

One of the cheapest approaches wehave found is to use the Pet (£695) plussome payroll programs (£25) which havebeen written for it by an accountant.Although you could run your payrollwithout a printer, it is much simpler ifyou have one and the cheapest is aroundthe £400 mark at present-total cost,around £1,200.

Hire serviceFor that you would have a system which

could handle up to 100 employees quitecomfortably. Above 100 employees it isprobably better to use a disc -based system,for which you would be spending up-wards of £2,000.

Payroll, of course, is not the only appli-

cation which a computer could run. Apartfrom playing games, you could run otheraccounting procedures on it, which helpsto justify its purchase.

As an aside, you can now hire disc -based computers for around £40 a weekand the resultant time -saving may well beworth the money.

The Pet payroll system is in two ver-sions: Series A is for machines with onlyone cassette deck and Series B is for twincassette deck operation.

The Series A suite will cope with 10employees per cassette tape. It will workwhether or not you have a printer and canhandle monthly or weekly -paid staff. Itcan accommodate two overtime rates,short time (unpaid leave), staff loans andautomatic deductions, and three NationalInsurance rates (A, B, or C).

The Series B suite will handle every-thing the A suite can do, plus hourly -paidemployees, three overtime rates, hourlybonuses, non-taxable expenses and up to100 employees per data tape.

The Series A suite of programs consistsof three parts-create and change, copyduplicate and print, and payroll. Createand change is used to create and updatethe employee data file. Duplicate allowsthe user to take a back-up copy of theemployee file on a separate cassette, so as

Postscript to MastermindTHE ARTICLE, "How to Play Mastermind",in our November, 1978 issue describedand presented a program for the 6502 -based KIM microprocessor system toplay the game Bulls and Cows, now betterknown as Mastermind.

Once the standard game has beenmastered, a simple modification will con-vert the program to play a much moredifficult variant of the game, known asParity Bulls and Cows.

In this version the guesser is not toldthe numbers of Bulls and Cows betweenhis guess and the code, but only whethereach of these is odd or even; the reply is"1" if the number is odd and "0" if it iseven.

Thus to a code string "0123" the replywould be "00" for the guesses "4567","3266", "0166", or even "3210", whereasin the standard game they would all bedistinguished by different replies. Whenthe guess is correct, the reply "40" mustbe given. The modifications are as follows:

022D 4C D6 0303D6 A5 D603D8 29 01O3DA AA03DB AS DS03DD 29 OS030F 60

IMP PATCHPATCH LDA COWS

AND GITAXLDA BULLSAND LSRTS

When playing Parity Bulls and Cows


the program needs, on average, about 10guesses to get your code string.

The graph showing the performance ofthe original Bulls and Cows program overa sample run of 1,000 games was acci-dentally omitted from the original article,and is now reproduced here. The programneeds on average 5.74 guesses and all thecodes were guessed in nine guesses orfewer.

Finally, an error occurred in the pro-gram listing; the data at 0200 should be:4C A8 02 (not 4C 48 02). The remainderof the listing as published is correct. al

to reduce the risk of losing valuable data.The print function is used to obtain a print-out on hard copy of any employee data.

Payroll performs the calculations. It isdone by typing -in the file name, thecurrent week number, the number ofemployees held on the tape, after whichthe program prints -out an employeename and asks for variable data con-cerning the employee.

Depending on your computing experi-ence of using the Pet and payroll, it isadvisable that you begin with the Series Aprogram, since it holds less informationand if, an operational failure shouldoccur, it will be easier to input data inagain in the Series A program than theSeries B program.

UpdatingThe system provides for placing output

on a printer as well as a VDU. The outputof the payroll program can be useddirectly to prepare payslips for the em-ployees on the data file. If you do not owna printer, it is suggested that you preparepayslips in the format of the printout onthe VDU, and copy the data as it appearson the screen.

Both programs are well -written, thoughrather complex to run. The complexityis not helped by the standard of the docu-mentation which, though reasonable, hasconsiderable scope for improvement. Weare informed, however, that new andimproved documentation is being written.

The programs require a great deal ofmanual manipulation which makes them,in computing time, rather slow. This,together with the complexity of runningthe program is principally the limitationof the complete system rather than thesoftware.

Despite these minor criticisms, theprogram should enable the businessmanwith a Pet to reduce considerably theamount of time spent on payroll, as wellas avoiding headaches due to excessivecalculation.

The author of the programs also runsan updating service to take into accountany new laws or changes to PAYE in-structions. It costs £10 a year.

37

Avoiding major itemsof expenditureFor the small development company or indeed for the amateur, mostof the microprocessor development kits require one major item ofexpenditure which can more than double the cost of a developmentsystem-the Teletype device used for the main human/micropro-cessor/human communication.

EVEN the 'glass Teletypes' (VDUs) nowbeginning to proliferate at lower costsare still not cheap enough by comparisonwith the cost of the actual user kit.

For example, it is possible to buyseveral micro systems at less than £500each, while a new ASR33 Teletype orSilent 700 terminal will cost more than£1,000 and a VDU will cost about £500.

The micro was designed as a simplereplacement for a box -full of TTL or evenmechanical logic in such applications ascontrol systems, amusement arcade gamesand intelligent data transmission systems.Obviously none of those products is likelyto use a Teletype as the I/O medium in thefinished article, so the use of a Teletype inthe development of such products is notonly expensive but also questionable.

Best approach

Bywood Electronics was confrontedwith the problem of getting its ownmicro units up and running and atthe lowest cost and although it had pro-grammers on the staff, they had only IBMexperience. It was decided eventually thatthe best approach was to take a micro chipand add as few extras as possible it to get aminimum system running, so that thecapabilities of micros could be investigat-ed.

This simple system used LED lamps toshow the status of the 8 -bit data lines, the12 -bit address lines and four single -bitI/O lines; so as not to load the MPUbusses unduly the LEDs were run fromCMOS drivers.

Bywood is a company which specialisesin the supply of LSI technology compon-ents to small -volume users. To ease thedesign of equipment based on thesecomponents, a set of simple kits wasdesigned for such things as digital clocktiming and counting circuits.

The typical customer was either anamateur constructor or a designer deve-loping a larger piece of equipment whodid not have the time or resources to inves-

38

tigate the chips from first principles.One of the first applications for its

own development kit, SCRUMPI, was tomake the I/O of instructions and data bymore experienced micro designers a littleeasier and faster. As the micro talks onlyin Hexadecimal codes, there are only 16numeric keys required (0-9 and A-F)plus a few operation keys such as RUN,STEP, RESET, and the like.

The digital LED type of display usedin some micro kits is limited by the num-ber of digits (usually 6 or 8) and the factthat the seven -segment type of displayseverely limits the number of under-standable non -numeric characters whichcan be displayed.

It sought a low-cost, quiet, legibleoutput device capable of displayingtextual messages which were not sostylised that a layman would have difficultyin understanding them. The idea of usinga video output to a TV monitor or com-mercial TV set is new and as it hadalready designed and sold several types ofVDU character -generation systems, itdecided to cost a minimum configuration.

Several basic units

This type of VDU contains severalbasic units:TV synchronisation signal generation.

This part of the circuit generates theline and frame sync signals used tosynchronise the 'picture' on the screen.It has to generate a line sync and thenecessary blanking signals every 6411sand the similar frame signals every20ms (figures refer to 625 -line TVs).

Within the visible 48µs horizontal timeit has to define a number of characterslots and similarly define a number ofcharacter rows in each visible verticalscan.

Within each character slot it has todefine a number of horizontal dots andvertical lines, each to include inter -character spaces.

Each character slot has to be able to dis-

play several (in fact, 64) characters,made up from light and dark dots andlines.

A memory is required to remember thecharacter required at each of all thepossible character locations defined inthe second item. This memory must beaccessible by the VDU and by theMPU.The keyboard has to be low-cost, simple

to assemble and use, but still give as manycharacter code inputs as possible.Bywood decided to run the keyboard asa 16 -key block, plus four 'mode' keysand an interrupt key.

Decoding by micro

The decoding of the code from the keydepression(s) was to be done by themicro rather than using an external en-coder to save on -costs, component countand to give maximum flexibility. Thus inthe end -product the designations of thekeys are controlled by the software andcan be labelled to user requirements.

One example uses the INT key tosimulate a Carriage Return/Line Feedfunction used to indicate the end of ahuman -to -micro command string or oper-ation. The 16 -key block is used to definecharacters in the 64 -character ASCII setand three of the mode keys define whichpart of the ASCII set the 16 -key blockdefines.

In this example it is possible to enter 65codes by use of only 20 of the 21 keysavailable. The keyscould be re -labelled forcontrol functions which are completelyunrelated to the ASCII character set.

Single address location

To the micro the port looks like a singleaddress location at which it can read orwrite data; the micro addresses the portphysically by decoding an address strobefrom the address bus. Any time that this



Peripherals

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address is accessed the strobe will becomeactive and thus inform the port that it isbeing accessed and should thus takeappropriate action.

To the engineer and to external equip-ment, the port looks like an 8 -bit TTLlatch. When used for output, the data onthe micro data bus is latched into the portand thus appears latched at the port out-put pins; from there onwards these out-puts can be assumed to have come fromany similar TTL type of device.

When used for input the port becomesan 8 -bit latch presenting its inputs to theexternal circuitry; usually one of the in-puts or an additional control pin acts asthe clocking input.

Interfacing

Data is presented to the port inputs andlatched by strobing the clock input; thedata at the inputs can then be released asthe data is now held in the port. At thesame time the micro is informed-orfinds out for itself-that there is new datain the port; it can thus 'read' the portaddress which will enable the port out-puts to deposit their data on to the databus and thus into the micro chip.

In applications of this type, the microwould then signal to the port that it hadread the data and that the port could in-

put some more. This sequence of "I've gotsome data for you", "Thank you, I'veread it" is called 'Hand -shaking'.

A very simple example of interfacing toa micro via a port is the type of hand con-trol used in TV games for 'bat position'.This is a simple potentiometer and as suchcannot be understood by a port or anyother TTL circuitry. To interface a poten-tiometer to a micro we can use a simplemonostable such as a 555 timer or a74123.

With this type of IC a trigger signalcauses an output signal to change state.After a time, this output will revert to itsoriginal state, the time being set by anexternal capacitor anctresistor network.

Taking an example of such a circuitwhere at one end of the travel of thepotentiometer the output changes statefor 100mS and at the other end the delayis 200mS, there is a variation of100mS. The trigger of the circuit is con-nected to a port input. The micro can thustrigger the monostable and then delay fora fixed time to compensate the first100mS. If the micro then performs aprogram loop which reads the port inputbit until the monostable output reverts toits original state, there is:START: Set Trigger.

Delay 99mS.Set Count to zero.

LOOP: Read input bit.If changed go to END.Add 1 to count.

Delay rest of 1 mS.Go to LOOP.

END: At this point count contains O.which represents a setting of thepotentiometer.

The count at the end can be used as avariable in a program, which can thusknow the current position of the potentio-meter and even its rate of change.

The potentiometer obviously can bechanged for any other form of variableresistor-thermistor, LDR, pressure trans-ducer-or in a similar manner withvariable capacitance, voltage or current.

Similar circuits in reverse can be used toallow a micro to output a variable voltageand thus perform such tasks as heat orspeed control, or something as simple asplaying tunes.

Simple tasks

The more usual output requirement isas a switched output, either as a pulsetrain or as a single ON/OFF switch. Thepulsed output can be used to input theTTL-type circuitry, such as a counterchain, for use in such things as IC testing.Here the CLOCK, RESET and LOADsignals can be simulated by the microwhich can also test the outputs from thecounters or other ICs and thus check aPCB or a single IC much faster than ahuman being.

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Circle No. 14139

PUPILS AT Longfield School in Kentchoose to stay regularly after schoolhours to use the school computer. Thatcaused a certain amount of jaw -droppingin the reporter we sent to Kent, not leastbecause her memories of her own school-days were rather different.

Longfield is a comprehensive with1,400 pupils aged 11 to 18; it will soonbecome an Upper School for 13- to 18 -year -olds. What makes it unusual is itsthriving computer department, character-ised by a high degree of pupil participation.

In June, 1977 the school acquired anASR33 Teletype as the first step to a linkwith the county computer. It was soondiscovered that this was unsatisfactory.The county computer was restricted to16 inputs at one time; timetable clasheswere inevitable; the method was clearlyunsuitable for mass -teaching. Childrenrequire an instant response or they loseinterest.

First stepThen, while on a trip to the U.S., maths

teacher Mike St John saw the Altair 880B.He promptly bought a kit and assembledit during the summer holiday. The systemwas completed with two cassette unitsand an ex-ICL 30 cps printer. On October27, 1977 the system was up and runningand the first program was keyed in-it wasa program written by a sixth -former toprint multiplication tables.

The next step was to obtain somepaper -tape punches, the aim being to givehands-on experience to as many children as

Question: How do you getchildren to stay willingly atschool until 6.30 p.m.

Answer: Get a computer.

possible. Hard copy of some kind is alsonecessary for examinations and assessment.

The Longfield method of acquiringextra equipment is remarkable. Very littlepublic money has been spent. Parentshave been able to help, either by givingthe odd roll of Teletype paper or byfinding donors of equipment; it seems thatbanks have been very generous, whichrather belies their public image.

St John explained that the school canaccept anything, modifying any piece ofhardware to run on its system. Not onlyhave people been generous with materials,they have also contributed a good deal oftheir time. For example, an ICL engineerwho lives locally carries out repairs.

The need to time-share led to theacquisition of a disc drive. Two SorocVDUs were also bought. They were allpaid for by writing software, for localbusinessmen and for Altair.

A payroll program was written forAltair. It was broken into modular units;the students dealt with the parts and StJohn put together the program. Altaircredits the school account, as it is notmoney but hardware which is needed.

The configuration now consists of the

Cilia ilia !I NI

Altair 880B (64KB memory), twin floppydisc drives, cassette units, the Teletypeprinter terminal, the ICL 30 cps printer,two display terminals and six off-linepaper tape punches.

St John explains that he chose theAltair because of its flexibility and multi-user capability. The system can support upto eight terminals and Altair is developingsoftware which will handle up to 20.

He would like to see a classroom ofpupils each with his/her own terminal."Less than that", he says. "is onlymaking do."

Full of praiseHe is also full of praise for the sup-

plier's "excellent service". The responsein cases of downtime has been immediateand thorough-vital where youngstersare concerned.

Installed in a classroom, the system hasthree functions within the school-as astudy in its own right; as a service toteaching; as an administrative tool.

The computer generates remarkableenthusiasm among the students. Theschool offers Computer Studies at 0level ; there are 28 on the course. In thesixth form. 14 students take computingas a "recreational" course.

Then there is a flourishing computerclub. Surprisingly for a modern compre-hensive, very few girls opt for computing;the one girl whose work was mentionedwas writing a recipe program.

In the computer club the pupils(continued on next page)


Education


examine the history and basic principlesof computing. They also learn whathappens inside and develop engineeringskills. Visits arranged for the eager hordesinclude the British Science Museum, theKent County Council mainframe, andtrips to offices and factories to see andcompare manual and computerisedmethods of administration.

All programming is done in Basic, apowerful language with the advantage ofbeing transferable easily between systems.

The computer room impressively organ-ised. It is run like any commercial dpdepartment, with a job specificationsheet; every group using the computerhas a system of job allocation. Forexample, each group has an environ-mental control officer, librarian, systemsmanager, software controller, suppliesofficer, and even a public relations officer.

In controlThe staff members involved try and stay

in the background and let the pupils "fireeach other with enthusiasm". GabrielleHayes, who teaches English, considersthe appeal of programming derives fromthe student's feeling that he or she is incontrol. The atmosphere in the computerroom is lively, relaxed and friendly-traditional staff -student relations have dis-appeared in this area of school activity.

The fact that the computer runs 12hours every school day must be someindication of its popularity. The studentsspend breaks, lunch hours, and after -school time keying -in and punching.

Children often write programs at home,not as homework, but on their owninitiative.

Around 6 pm St John insists the systembe handed over to him and GabrielleHayes, so that they can work on develop-ing the computer's second role, that of ateaching aid.

Miss Hayes first had the idea of teaching

through computers when she was workingwith disadvantaged children. She foundthat the stimulus of a computer resulted inreal progress. With a child of any ability,the use of a computer, especially with aVDU, increases the pupils' attentionand develops powers of concentration.

Moreover, the novelty of working witha computer pays off. Children behave forthe reward of a turn at the keyboard.Also, as headmaster Harold Darbypoints out, computers have the samepotential as typewriters in encouragingEnglish skills.

Gabrielle is working on programs to be

used in teaching English. Preliminarywork has been done on the teaching ofspelling, a lesson, she says, which that canbe boring and repetitive.

Spelling lessonsIn any teaching program the first step

is to familiarise children with the key-board. The spelling lesson begins with anapparently easy exercise-write the alpha-bet.

A second exercise involves the placingof prefixes and includes an element ofreinforcement when the student is askedto select definitions for the words he orshe has just constructed. In all theseprograms, if a student makes more than acertain number of mistakes, he or she istold by the computer to return to teacher.

As a result of using the computer,children accept that they must spellcorrectly-unlike a teacher, the machinedoes not understand approximations.

The teaching programs have alreadyinterested publishers but the staff involvedexpress the need for more time.

The third function of the school com-puter is to help with administration. Theschool houses a branch of Barclays Bank-accounts are handled by the computer.Course options and form lists are alreadycomputerised and it is intended to haveall the school roll on the computer.

A student is writing a program for thedeputy head which will cope with thetime-table-listing staff, classes, androoms.

Pictures by Longfield sixth former DavidWhitehead.

41

Basic program tooperate interface

by ROLAND PERRY

LAST MONTH we looked at the hardware interface required toconvert IBM Selectric typewriters into computer terminals and theprinciples behind the conversion. Part II describes a program inBasic (fig A) which accepts data in ASCII form, and operates theparallel interface to the Selectric driver electronics.

FIRSTLY, a code conversion is performed, using a look -up tableand then the protocol of the handshake interface is followed.The Basic is fully commented, and the reader should follow itthrough for both a golf -ball and a non -golf -ball operation. Sub-routine 20000 is called only once to set-up the look -up table,whereas subroutine 10000 outputs each string.

Note the carriage return code added to the string in line 20.As was mentioned in Part I, the Basic is given only to describethe program structure required, as it will run at only a fewcharacters per second, causing both a slow print speed and anunnecessary amount of wear on the printer mechanism.

The subroutine should be converted in machine code for thecomputer hosting the terminal, and an example (fig B) is givenfor the Micropolis operating system running in a 32K 8080

The circuit diagram (figure II) printed last monthwas incomplete. The amended version, along withthe power supply for easy reference is printed below.

+5V

r......,/ROM TIMINGCONTACTS

IN 10

IT2ANO TAB)

To furthergates

BS (CR AND en)

B (TI AND LF)

RD (RSA AND S)

(TI AND BSP)

BI (112 AND SO

a. (01-6 ANDS)

MONOMMELE

1V

BISTABLE

KO 10 TRANSISTOR(TART

0 TRANSISTORtT,/

microprocessor. Before running the driver routines the statement"MEMEND 16R7E7F" must be used to protect the uppersection of memory from the Basic User space, otherwise a largeprogram might over -write the drivers. The look -up table occupies7E80-7EFF and the program 7F00 -7F68, plus a few overlays forthe existing MDOS printer routines.Next month: modifications to the system for use as an input device.

Figure A. The BASIC.READY

LIST10 GOSUB 2000020 (4,"THIS IS H TEST

GOSLC 1000040 END50

60

10000

10010100201002010040

10050

10060100701008010090101001011010120101201014010150

1016010170

1018010190102001021010220 CB=C(C.9)

Power supply.

ME' ,MGE u+CMRPf.,16ROD)

THE SUBROUTINE CONVERTS ASCII VALUES FROM THE STRING C$INTO IBM CODES, DIFFERENTIATING BETWEEN GOLFEHLL ANDNON-GOLFBALL CHARACTERS. fi SHIFT OPERATION IS PERFORMEDIF REQUIRED.

PORT 54 HEX <DESIGNATED 161054 IN MICROPOLIS BASIC) IS THEPARALLEL I/0 FORT USED. BIT 7 OF THE OUTPUT (DECIMAL 255SIGNALS THE HRNDEMAKE AND TYPE OF PRINT CYCLE. BIT 7 OF THEINPUT GIVES THE CASE OF THE FRUITER - OFPER OR LOWER - ANC.BIT 0 (IF THE INPUT WHEN ZERO INDICATES THAT THE PRINTER ISBUSY

THE MICROPCtIS BASIC. FLNCIION .FFMC' RETURNS THE FRACTIONALFART OF a DIVISICN, IE THE REMAINDER J AND WOULD EE REPLACEDBY A SHIFT-RIGHT-INTO-CARRY IN A MACHINE CODE PROGRAM.

C9=0SC(MIDS(C$,19,1)) ! SELECT X9 TH. CHARACTERIF 1971.6.821 THEN 10480 I JUMP IF NON-PRINTABLE CHARACTER

! HERE IF PRINTABLE CHARACTER

! LOOK UP IBM CODE IN TABLE

(continued on next page

MAINS

INPUT

Figure II42 PRACTICAL COMPUTING February 1979

IBM typewriter conversion


10230 IF C9=0 THEN 1045010240 IF C62,127 THEN C8=C8-12816010 10330

1025010260 IF INA6R54)<128 THEN 104001027010280 IF FRACAN(16R54)(2)=0 THEN 1028010290 OUT(16R54)=25510300 OUTA6R54=12710210 OUT(16R54)=25410220 Gcao 10400

1011010340 IF IN(16R54)_:127 THEN 1040010350 IF FRACAN(16R54)/2=0 THEN 1015010360 OUT(16R54)=25510170 OUT(16R54)=12710380 CUT(16R54)=253103901040010410

10420 IF FRAC(IN(16R54)/2)=0 THEN 1040010410 OUT(16R54)=25510440 OUT(16R54)=127-C810450 NEXT X910460 RETURN104701048010490105001051010520

105301054010550200002001020020200302004020050200602007020080

20090201002011020120201302014020150

201602017020180

201902020020210

202202022020240

202502026020270

202802029020300203102032020330

READY

IF C(59'=0 THEN 10540IF FRAC(IN(16R54)/2)=0 THEN 10500OUT(16R54)=255OUT(16R54)=127OUT(16R54)=255-C(C9)NEXT X9RETURN

! THE SUBROUTINE SETSWITH VALUES IN HEX

DIM C(127)

ASCII 1 TO 7DATA 16800,16R00,16R00,16800,

! ASCII 8 TO 127DATA 16R04.16840,16810,16R00,16R00,DATA 16R00,16R00,16R00,16R00,16R00,DATA 16R00,16R00,10400,16R00,10400,DATA 16R08,16RBE,16R9C,16RFC,16RD8,DATA 16RF0,16RD4,16RFR,16RFF,16R29,DATA 16R54,16R7F,16R7A,10456,16R75,DATA 16R79,16R70,16R80,16R00,16R00,

DATA 16RF5, 16R99, 16RC0, 16RC9, 16RED.

DATA 16RE4,16868,16R8E,16RE8,16RC5,DATA 16RAC,16R88,16RE0,16R64,16REE,DATA 16RCF,16R84,16RDE,16R00,16R00,DATA 16R75,16819,16R40.16R49,16R6D,DATA 16R64.10438,16R0E,16R68,16R45,DATA 16R2C,16R08,16R30,16834.16R6E,DATA 16R4F,16R04,16R58,16R00,16800,

FOR N= 1 TO 127READ C(N)NEXT N

OUT(16R54)=255OUT(16R54)=127OUT(16R54)=222

RETURN

IGNORE IF NOT ON GOLFBALL:! MODIFY AND JUMP IF UPPERCASE

! HERE IF LOWERCASE REQUIRED! JUMP IF PRINTER IN LOWERCASE

! HERE TO PUT PRINTER IN LOWERCASELOOP WHILE PRINTER BUSY

.! RAISE HANDSHAKE LINE (BIT 7)

.! LOWER HANDSHAKE LINE:! OUTPUT SHIFT -TO -LOWERCASE CODE

' HERE IF UPPERCASE REQUIRED

! JUMP IF PRINTER IN UPPERCASE! LOOP WHILE PRINTER BUSY' RAISE HANDSHAKE LINE

1' LOWER HANDSHAKE LINE! OUTPUT SHIFT -TO -UPPERCASE CODE

! MAIN GOLFBALL PRINT ROUTINE

LOOP WHILE PRINTER BUSY:! RAISE HANDSHAKE LINE

' OUTPUT PRINT CODE (INVERTED):! NEXT CHARACTER

! MAIN NON-GOLFBBLL PRINT ROUTINE' JUMP IF UNPRINTABLE CODE-! LOOP WHILE PRINTER BUSY

! RAISE HANDSHAKE LINE:! LOWER HANDSHAKE LINE.! OUTPUT PRINT CODE (INVERTED)

.! NEXT CHARACTER

UP THE LOOKUP -TABLE CIF CONVERSION CODES

FOR ERSE OF INTERPRETATION.

16R00,16R00,16R00

16R20,16R02,16R0116R00,16R00,16R0016800,16800.16R0016RA5,16RD0,16RIC:16820,16R1A,16REB16R7C,16R58,16R5D16R2A,16800,16RAA

16RCC,16R86,16RAF16R9F,16RCA,16R9516REBA.6RBB,16R9016R00,16R00,16RAO16R4C,16R06,16R2F16R1F,16R4A,16R1516R66.16R36,16R1016R00,16R00,16R00

INITIALISE PRINTER

Figure B. The 8080 machine code.

0000 LINI SYS01-

00000000 ORG 7E8OH7E80 00 00 00 DO 00H,O0H,00H,0011,00H,00WOOH,00H7E83 00 00 007E86 00 007E88 04 40 00 DB

7E8B 00 00 207E8E 02 017E90 00 00 00 D6

7E93 00 00 007E96 00 007E98 00 00 00 DB

7E9E: 00 00 007E9E 00 007EA0 08 BE 9C DB

7EA3 FC. D8 A5

7E06 DD 1C.

7EA8 FO D4 FR DB

7EAE FF 29 20

?ERE 1A EB7E80 54 7F 7A DB

7E83 58 75 7C7E66 58 507E88 79 70 8D DB

7EBB OD 00 2R7EBE 00 RA7ECO F5 99 CO DB

7EC3 C9 ED CC7E56 86 RF

7EC8 E4 68 8E DB

04H, 40H, 00H, 00H, 00H, 20H, 02H, 01H

00H, OOH, 00H. 00H, 0811. 00H, 00H. 00H

00A, 00H, 00H: 00H, 00H, 0011, 00H, 00H

08H, OBEH, 9CH, OFCA, 008H, OA5H, ODDH, 1C-14

OFOH, 0D4H, OFAH, OFFH. 29H, 20H. 1AH, OEBH

54H, 7FH, 7AH. 5BH, 75H 1H,58H,5DH

79H, 70H, 8DH, 00K, 00H, 2AH. 00H, ORM

0F5H, 99H. KOH. 0C 9H, OEN, &CH, 8811, OAFH

00411, 80811, 8E1-1. 0E8H, 0C5H, 9FH, OCFIH, 95H


7EC6 E8 C5 9F7ECE C:A 95

7EDO AC 88 BD7E03 84 EE EB

7ED6 BB 907E08 CF 84 DE7EDB 00 00 00

7EDE 00 A07EE0 75 19 407EE3 49 6D 4C

7E06 08 2F7EE8 64 38 OE7EEB 68 45 1FIEEE 4A 15

7EF0 2C 08 207EF3 14 6E 667EF6 38 107EF8 4F 04 5E7EF8 00 00 00

7EFE 00 007F007F007F00 CD 53 7F IBMOUT

7F83 D57F04 787F05 C6 807F07 5F7F08 16 7E

7FOR 1A7FOB EE 007F0D C:A 51 7F

7F10 577F11 787F12 FE 21

7F14 FR 4D 7F

7F177F17 7A7F18 FE 80

DO. MCA. 88H, OBE)H.. 0B4H, OEN. OEBH. OBBH, 9011

DB OC.FH, 8411. ODER. 0011, 00H, 00H, 00H. 0.A01-1

DO 7511. 1911. 40H. 49H, EDH, 4CH, 0811. 2FH

DB 64H. 3811, OEN, 69H, 45H. 1FH, 4A14. 15H

DB 2CH, 08H, 3DH. 34H, 6EH, 6611, (OH, 1014

DO 4FH. 04H. 50-1, 00H, 0011. 00H. 00H, 00H

ORG 7FAOHCALL BUSY ;TEST M/C

FINISHED LAST CYCLE

.SAVE D/E REGISTER:ASCII TO A,FORM LS BYTE OF LU TABLE.ADDRESS IN E (ASCI1+80 H).MS BYTE OF ADDRESS TO D

.GET IBM CODE INTO A,DUMMY TO SET CONDITIONS.ZERO IBM CODE SIGNIFIES NO -OP

;SAVE IBM CODE IN D;ASCII TO A

;IS IT AN OPERATIONAL CYCLE

* THIS ROUTINE OUTPUTS A PRINT CYCLEMOV A,D ;RETURN IBM CODE FROM DCPI 80H ;GREATER THAN 80H

SIGNIFIES OFFER CASE

PUSH

MOV

ADI

MOV

MVI

LOWXRI

JZ

MOVMOVCPI

JM

0

A, El

80H

E.0

0, 7EH

09HEND

0. R

A, B

21H

OPCYCLE

7F1A F2 2F 7F JP UPPERCASE

7F1D * HERE IF LOWERCASE PRINT REQUIRED7F1D DB 54 IN 5411

7F1F E6 80 RAI 80H

7F21 CA 41 7F JZ PRINT .ZERO INDICATES MA: IN LC

7F24 06 01 MVI 6,01H ABM CODE FOR SHIFT DOWN

7F26 CD 56 7F CALL OPPRINT

7F29 CD 53 7F CALL BUSY

7F2C C3 41 7F JMP PRINT

7F2F *HERE IF UPPERCASE PRINT REQUIRED7F2F DE 80 UPPERCASE S.61 80H .REMOVE MSB FROM IBM CODE

7F31 57 MOV D,A ;REPLACE IBM CODE IN D

7F32 DA 54 IN 54H ;TEST CASE BIT

7F34 E6 80 HMI 80H

7F36 C2 41 7F 3142 PRINT

7F39 06 02 MVI 6,02H7F3B CD 56 7F CALL OPPRINT

7F3E CD 53 7F CALL BUSY

7F41 3E FF PRINT MVI A,OFFH

7F41 D3 54 CUT 54H

7F45 7A HOY A,D

7F46 EE 7F XRI 7FH

7F48 D3 547F4A C3 51 7F7F4D 427F4E CD 5B 7F7F517F52 C97F53 DO 547F557F577F5A7F587F5D7F5F7F617F637F64

E6 01CR 53 7FC93E FF

D3 543E 7FD3 5478

EE FF

7F66 D1 547F68 C97F69

7F69

06CB0603 C3 00 7F

06CE06CE

06FE

06FE 06 OD0700 CD 03 7F0703 06 OF0705 CD 03 7F

0708 06 OE070A CD 03 7F070D 06 OF070IF CD 03 7F0712 AF

0713 C90714071406E8

06E8 AR06E9 C906EA

06ER

OPCYCLE

END

BUSY

OPPRINT

OUT

JAR

MOVCALLPOPRET

IN

RNIJZ

RETMVI

OUT

MVI

OUTMOV

XRI

54HEND

13,0

OPPRINT

54H01HBUSY

FI,OFFH

54HA. 7FH

54HA. B

OFFH

OUT 54HRET

*ORG 06CBH

*THIS ROUTINE WILL OVERLAY LDOUTJAR IBMOUT

ORG 06FEH

*THIS ROANE WILL OVERLAY. LDINITMVI 6,0DHCALL 7F03H

MVI

CALL

MVI

CALLMVI

CALLXRARET

B. OFH

7F03H

111,0EH

7F03HB. 0FH

7F03H

ORG 06E8H

*THIS ROUTINE WILL OVERLAY LDATNXRA A

RET

END @WARMSTART;

.TEST CASE BIT

.WAIT FOR END OF OPERATION

;1 INDICATES M/C. IN U;IBM CODE FOR SHIFT UP

;WRIT FOR END OF OPERATION;RAISE STROBE LINE

ABM CODE TO A,COMPLEMENT

IBM CODE, BIT 7=0;WHICH LOWERS STROBE LINE

;IBM CODE TO B

,TEST BIT 1

;RAISE STROBE LINE

;LOWER STROBE LINE

;IBM CODE TO A;COMPLEMENT IBM CODE,

BIT 7=1

;CARRIAGE RETURN;DO AN OUTPUT

;SHIFT DOWN

;SHIFT UP

;SHIFT DOWN

JUMP TO WARMSTARTMOOS. NITIALISE I/O

43

Introducing the personalcomputer you've waited for.

The Exidy Sorcerer.

The Sorcerer Computer is a completely assembled and testedcomputer system ready to plug in and use. The standard configura-tion includes 63 key typewriter -style keyboard and 16 key numericpad dual cassette I/O, with remote computer control at 300 and1200 baud data rates, RS232 serial I/O for communication,parallel port for direct Centronics printer attachment, Z80 pro-cessor, 4K ROM operating system, 8K Microsoft BASIC in separateplug-in Rom Pacw cartridge, composite video of 64 chars 30lines, 128 upper/lower case ASCII character set and a 128 user -defined graphic symbols, up to 32K on -board RAM memory,operators manual, BASIC programming manual and cassette/video cables, connection for 5100 bus expansion unit givingaccess to the spectrum of exciting and useful peripheral devices,such as Floppy disk drives, voice recognition/synthesis batteryback-up board in case of power failure, additional memory boards,E -PROM cards give you the facility to program and re -programyour own ROM memories etc. etc. This is the most useable andflexible system that's now available to the home and business userat such a low price.

16K .2760

K AT THESE FEATURES add 8%32K E 859

VATWORD PROCESSING, COBAL, FORTRAN etc

* PLUG IN ROM CARTRIDGES

* WORKS WITH NORMAL TV

* S100 EXPANSION UNIT JADE* CASSETTE INTERFACE

* Z80 CPU

* 32K RAM ON BOARD

* A REAL BUSINESS MACHINE

Supplied by - Factor One Computers

SEND 50pFOR LATEST

CATALOGUE,ermon

contains anintroduction toMicrocomputer.etc.

please make cheques and postal orders payable to JADEphone your order quoting ACCESS or VISA number

technical information advice 66565

17 Market Place, Penzance,Corrxwa11. Circle No. 142

DE BOERELECTRONICS

Our program contains a large assortment of kits. Speciallyinteresting is a microprocessor kit designed by Elektormagazine. This SC/MP µP (National Semiconductors)consist of:

RAM 1.0 (9846-1), digital in- and output. With binaryswitches -displaying the databus £32.35

SC/MP board (9846-2), a simple mainboard. With the!AP- and timing circuits £26.75

With these two kits you can start your own "µP-ing-

CPU -card (9851) extension card for the SC/MP. Thiscard contains the SC/MP (you don't need the SC/MPboard anymore) E- prom for monitor, some RAM etc. £90.50

Bus -board (9857): Handy card to connect to SC/MPunit in an easy way £3.00

TrEiNei"-roz!

00 00,

Memory card (9863): This card completes the heartof the kit. With some memory and monitor E -proms £57.00

Hex 1.0 (9893): Now you can load your program inhex -code and on the card there are hex displays £67.25

4-K RAM (9885): memory extension £112.05

SC/MP power supply (9906) with transformers £23.05

Cassette interface (9905): This kit makes it possible tostore programs in an easy way. You can use an ordinarycassette -recorder £16.05

3 Elburg-programmed Eproms £68.85Complete system, consists of 9851-9863-9885-9906-9905and Elburg Eproms £349.00

Keyboard complete with encoder £46.50

Video display terminal (accepts information of keyboardand SC/MP µP)

Ordering details:By letter to: Mike Hutchinson, 2 Lynn Road, Grimston,Kings Lynn, Norfolk PE32 1AD. Phone: Monday to Friday1 pm to 6 pm. Saturday 10 am to 1pm. At Hillingdon(04856) 553 cheques and postal orders only in the nameof De Boer Electronics. All prices are VAT -inclusive.Add 50p for post and packing. No callers, please.

44

lel U40 448229

£69.00

r de boerelektronika

Kleine berg 39-41 Eindhoven

CircleNo. 143


WITH so many varied activities in a university city, operating acomputer shop demands versatility. Cambridge Computer Storeprovides it for a broad spread of customers.

All this and a farmfeed program, too

IN Emmanuel Street, Cambridge, notfar from King's College and its impressivechapel, there is a small computer shopowned by Claude Cowan, which mayseem a trifle out of place.

"On the contrary, it's natural to behere", says Cowan. "Being outsideLondon has not affected business at all;as a matter of fact, we are doing extremelywell. In Cambridge we have some of thefinest physics and maths laboratories inthe world. The university also has acomputer laboratory where extensivesoftware and hardware development istaking place. Cambridge is a fertile areafor computing activity, and I could notconsider being anywhere else!"

So be it. Cowan obviously must be sureof himself. His background stretchesfrom university days when he graduatedin electronics. Since then, he has workedas a systems engineer with extensiveinvolvement in VDUs and now runs hisshop while, at the same time, acting as acomputer consultant.

How did he become involved withmicrocomputers? "I was thrown into it",he says.

His shop, before it became CambridgeComputer Store, started as a modestTandy electronics outlet in November,1975. It sold assorted audio hi-fi equip-ment, calculators, hobbyist electronickits and a selection of electronic com-ponents, such as resistors, transistors andcapacitors.

Gradual expansionThe shop expanded gradually, offering

a wider range of electronic equipment,and microcomputers followed. Soonafterwards, a separate department evolvedwithin the Tandy store until it changed itsname.

"It all happened rather suddenly",says Cowan. "What many people do notrealise is that even though micros arejust breaking the ice in this country,computing has been going on for a longtime. There has been a large amount ofresearch devoted to the subject and a

great deal of it is taking place right here-in Cambridge."

One would tend to think that being in.the "centre ring" of computer activitydemands certain exceptional qualifica-tions. Cowan feels he has them. Hestresses the importance of being able tooffer the customer what he calls "a pro-fessional level of support."

"When someone enters the shop,whether a beginner, businessman, student,hobbyist or professional, we want him tofeel comfortable. Our shop is small. Wecarry three systems-Apple II, TandyTRS-80 and North Star Horizon-but wefind each system to be an excellent choicefor a particular market. The Apple II is anexcellent machine for educational pur-poses. while the North Star system acts asa powerful business machine.

Tandy is favourite"The Tandy TRS-80 is our favourite

and works well in education, business,home use and recently in farming forwhich we have developed a softwareprogram, Farm Rationing."

Cowan has written a program which de-termines proper rations of feed for dairycattle. It has two parts. The first is RationFormulation which allows the operator toprepare a trial ration. He does this byselecting 13 ingredients, like wheat, corn,barley and maize from a possible 25 tomake up a particular ration of feed forhis cattle. When he has chosen theingredients and decided he has enough fora trial ration, he enters the cost of eachingredient, as well as the amount and theformulation program, and begins toproduce a trial ration analysis.

The analysis shows the operator theresulting chemical percentage composi-tion, the energy content and the cost ofthe trial ration. The results are displayedinstantly on the screen and if this is notthe optimised ration-not enough energyor too high a cost-the operator canalter the mixture until he has the desiredration. When he is satisfied, the programcalculates the mixture and cost of the

ration, and displays the results on thescreen.

The second part is the budget forecastwhich prepares a schedule of ingredientrequirements which will be needed over asix-month period. It can cover a herd ofcattle and divide the herd into groups.Each group may require a differentration, since groups of cattle calve atdifferent times.

In turn, each group goes through acycle of rations. The program can alsoaccount for ration changes which may nolonger be optimum in any particulargroup.

The program takes all informationweek by week for each particular groupand works out the weekly requirement ofeach ingredient and also the total require-ment over a six-month period.

This is an excellent example of the fulluse of a micro system such as the TandyTRS-80 video screen. The file storagecapability of the machine is used forrecording chemical cost and energycontent and its high-speed processingpower carries -out ingredient analysis usingthree-dimensional array multiplication.

More developmentFarm rationing requires a tremendous

amount of computation. By more usualmeans, it would take at least a day or two.Using the micro program -it is completedin five or six minutes. The program is inuse and working effectively at Attle-borough Dairy Farms in Norfolk.

Cowan speaks highly of the TandyTRS-80. He sees it as a "fine piece ofdesign with excellent, serious applicationuse."

The shop plans to do more softwaredevelopment and has already added a full-time programmer to the staff to work onthe Tandy and the ANA II.

Anyone is welcome to visit the shop forhands-on experience. It offers a variety ofinteresting demonstrations with a goodselection of books and magazines, andmost important of all, has professionalexperience.


O

WE LOOK at an idea this month for a gamecalled Warlock Warren and detail an approachto setting it up on your system.

Warlock Warren"SOMEWHERE nearby is Colossal Cave,where others have found fortunes intreasure and gold, though it is said thatsome who enter are never seen again.Magic is said to work in the cave. I will beyour eyes and hands. Direct me withcommands of one or two words.

"I know of places, actions and things.Most of my vocabularly describes placesand is used to move you there. To move,try words like forest, building, down-stream, enter, East, West, North, South,up, or down. I know about a few specialobjects hidden in the cave. These objectscan be manipulated using some of theaction words that I know.

"The objects have side effects, forinstance, the rod scares the bird. Usuallypeople having trouble moving just need totry a few more words. Usually peopletrying unsuccessfully to manipulate anobject are attempting something beyondtheir capabilities and should try a com-pletely different tack.

"You are standing at the end of a roadbefore a small brick building. Around youis a forest. A small stream flows out of thebuilding and down a gulley."

Thus reads the preamble to Adventure,a program at present residing on Digital -10 systems all over the country, and aparent of the program here devised forApple.

D&D elementCognoscenti of the games world will

recognise an element of Dungeons andDragons (D&D) in the invitation. In-deed, the lineage of Warlock Warren hasthe fantasy/role-playing class of games atits head.

D&D games have a free format inwhich players select the character theywish to assume and form an expeditionparty to seek adventure and treasure in alabyrinth of dungeons. The dungeons aredevised by a gamesmaster, who does not doany exploring himself, but instead takesthe part of umpire, or god.

In his design, the gamesmaster incor-porates various undisclosed rules. Duringthe game he describes to the players thesituation in which they find themselves.They then decide what to do, using theirimagination to any degree they choose,and he informs them of the outcome oftheir actions.

The gamesmaster's function includes a

by T. J. Radfordconsiderable amount of book-keepingand he is usually aided by dice of various"sidedness" and a pocket calculator. D&Dhas a wide and often fanatical following.

Here our geneology divides. In onebranch of the family, computers are intro-duced to assume the role of gamesmaster.In the other, standard formats for thedescription of dungeons, characters andevents are used to obviate the need for thegamesmaster entirely.

The first of the branches contains,among others, the game Adventure,originating at Stanford Research Institute.As indicated in the preamble to the pro-gram, the user is placed near a cave whichhe must locate and explore. There arehazards to overcome and there is treasureto collect.

Meeting strangersThe program, like the D&D gamesmas-

ter, describes to the user the situation he isin and he must guess the best action totake. For instance, at one point he is con-fronted by a snake. If he has caught thebird, encountered earlier, releasing it atthis point drives away the snake.

The same ploy, applied to the dragonguarding the Persian carpet, results in thepoor bird being reduced to a cinder. Thedragon has to be overcome bare-handed.

The other branch of the family in-cludes an interesting games calledSorcerer's Cave. Again, the theme is theexploration of a cave. Unlike other gamesin this category, the cave is not pre-determined.

By means of a large pack of "cavecards", the cave grows as it is explored.Each player, in his turn, chooses a direc-tion to explore, takes a cave card from theface -down pack and places it in the chosenposition.

A second pack of cards is used to revealthe presence of treasure, artifacts or"strangers", or may imply some randomevent, such as a cave-in which blocks theretreat.

A complex system of rules governshow strangers may be treated, whattreasure may be carried, the use of arti-facts and the interaction between players.

The two cognate lines meet again at theprogram here proposed. Both Adventureand Sorcerer's Cave can be fascinating

and very distracting. A disadvantage ofAdventure is that the cave is fixed. Onceit has been explored fully and all thepoints have been gleaned, its interestwanes. All one can do is to try to obtainanother program in the same family.

Another disadvantage is that it isstrictly solitaire, omitting all element ofcompetition. The Sorcerer's Cave formatsuffers from neither of those deficiencies.The game equipment, however, is some-what unwieldy. Players find themselvescrawling around large areas of floor,trying not to step on the cave cards.

Warlock Warren is intended to elimi-nate those disadvantages, largely using theformat of Sorcerer's Cave, but applyingthe computer to the task of manipulatingand displaying the game equipment.

ScenarioThe warren is a series of caves created

by a warlock as a repository for his ill-gotten gains. There, treasure and potentartifacts are guarded by a variety ofcreatures, though not all of these are thewarlock's minions. Players form separateparties and set out to explore the caves.

In the course of exploration, "stran-gers" may be encountered, who maychoose to join the search party. Eachmember of the party may carry a certainamount of treasure and any number ofartifacts. Points are associated with allbeings in the party and all treasure andartifacts. The player to regain the surfacewith the most points wins.

The program begins by asking for alist of the opponents' names and chosencolours. It allocates randomly the playingorder and then asks each player in turn toselect the composition of his party. This isdone using a "menu", the player enteringthe numbers which correspond to thebeings chosen.

Once the search parties are constituted,the game proper begins. Each player inturn is shown a map of the level on whichhis party is located, initially the first level.The map displays only that part of thelevel which has already been discoveredand indicates the position of any party onthe level, by colour.

Figure 1 shows a portion of such a map.Beneath the map, the lines of text willsummarise the status of the currentplayer's party, giving the number of

continued on next page)


wanes

continued from previous page)

beings in the party, their total physicalstrength, magical strength and sparecarrying capacity.

There may be up to six exits from thelocation-North, South, East, West, upor down. The player may indicate thedirection in which he wants to move byentering the appropriate initial letter.

Regular gridThe warren exists on a regular grid.

Grid points can be either caverns or thetunnels which serve to connect caverns.Strangers, treasure and artifacts arefound only in caverns and the few randomevents which may afflict a party can occuronly on entry to a cavern.

If the section entered is a cavern, theturn continues. Any random event hap-pens immediately.

Random events are relatively rare andonce they are dealt with, a summary of thecontents of the cavern is added to the textlines, giving the number of strangerspresent, their total physical and magicalstrengths, the probabilities of their beingfriendly, indifferent or hostile, respective-ly, the total value and weight of anytreasure, and the number of artifacts.

The player may obtain a completedescription of everything in the cavern byentering the command MAGNIFY. Allcommands are entered by initial letter.

The player may elect to GREET anybeings encountered. The program deter-mines their reaction based on the pro-babilities of their being friendly, indiffer-ent or hostile. If they are friendly, they

join the party. If they are indifferent, theturn ends and the player has the sameoptions on his following turn. If they arehostile, combat ensues.

The player may choose to engage thestrangers in combat, issuing the ATTACKcommand. The opposing lines are drawn -up and the program determines the resultof the combat. Any strangers surviving theonslaught remain hostile to the party andmust be destroyed before any treasuremay be taken. They may be attacked againon the following turn.

Certain artifacts may be deployed incombat, although some of them may beused only once during the game, afterwhich their associated points will notbe included in the final tally.

The player may choose to RETREATfrom a strong group of strangers. This isdone on the same turn as he entered thecavern, and the player must leave by theway he went in.

If there are no strangers present, orthey have all joined the party or beenkilled, the CARRY command may begiven. Any being in the party with spare

Figure 2 Cavern.

carrying capacity may be assigned treasureand artifacts.

It is anticipated that most of the codewill be written in Basic. Some of thedetails of representation, however, are atbit level and certain routines will thushave to be implemented at machine level.All frequently -performed routine taskspreferably should be written at low levelas well.

One such task is the generation of ran-dom numbers, which are used to deter-mine warren topology, cavern occupancyand combat results. This will employ astandard modulo -arithmetic, psuedo-random number generator.

The programming of WW breaks -downnaturally into six sections. They are con-cerned with the topology of the warren,random events, thecontents of thecaverns,combat resolution, various extra com-mands and overall control.

The representation of the warren mustdefine the connectivity of the cave andpermit discrimination between tunnelsand caverns. As the cells lie on a regular,three-dimensional grid, the warren can berepresented by an array. Each elementneed indicate only whether or not thecell has yet been opened, and if so,whether the cell is a cavern or a tunnel,and in which directions movement ispermitted. This information can be con-tained in a single byte, as follows.

Bit Function7 Area previously explored (bit set).6 Cavern (set)/Tunnel (clear).5 North4 South3 East2 West Way open if bit set.

I Up0 Down

The total size of the warren dependsultimately on the amount of memoryavailable. Another consideration is thatcertain entities have to contain reference totheir location, and it might be desirable tolimit the warren size to four levels, each ofeight cells by eight. This would permitlocation information to be contained in asingle byte.

For display purposes, each cell willoccupy 5 x 5 colour -coded display points.The two kinds of cell are shown in figure2. Green points represent space and bluepoints represent rock. Stairs occur only intunnels and are red points. Their positionin the display indicates their direction.The cells in figure 2 have all ways open.Closed ways are depicted as rock, thus the


Figure 2 Tunnel


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Circle No. 144


tunnel shown in figure 3 below has onlyNorth and West open, and an Up stair.

In the display, the boundary points ofthe cells can overlap, giving rise to mapssuch as figure 1. In this way, each celloccupies only 4 x 4 points on the screen,so for display purposes the limit on thesize of each level, without "windowing",is 10 x 10 points.

Cells are generated only when this isnecessitated by the entry of a party. Theopen ways of established adjacent cellsdetermine some of the cell bits. Theremainder are determined randomly,according to probabilities which will haveto be "tuned" by experiment.

The occurence of a random eventimplies some non-standard modificationof the state of the game. As such, eventsare best represented by sections of pro-gram which perform whatever interac-tions and modifications are required.

Two kinds of eventThere are two kinds of event. Some

have immediate effect only, while othersremain latent in the cavern and affect anyparty to venture that way. For example,a cave-in modifies the cave topology,creating an impassable cell, and is there-after inactive, although the modificationis permanent. A trap, however, remains inthe cell in which it occurred, affecting allparties which enter.

When a party enters a new cavern, theprogram determines whether or not arandom event is sprung. The probability islow, but if so, it then determines whichevent it is. A small array is used to recordthe location of recurring events. Thisarray is consulted every time a partyenters a cavern and the appropriatesubroutine is applied whenever indicated.

When a cavern is entered for the firsttime, its contents are determined. It maybe occupied by a collection of creatures,treasure and artifacts. The number ofoccupants will correspond to the level onwhich the cavern is located.

The information required about thecreatures and objects can be separatedinto specific information about each one,and general information about classes ortypes. The specific information needed isthe location and state of each entity. Thestate of an artifact or piece of treasurerefers to the creature carrying the objectThe state of a creature is a byte carryingthe following information:

Bits Function7-6 Party in which creature travels.5 Creature dead.4 Creature asleep.3-0 One bit per player: Creature hostile if bit

set.

The general information held abouteach type of creature or object is tabulat-ed:

CreaturesName Identifying string.Points Contribution to the final tally.



Games


FriendlyIndifferentHostileStrengthMagicCapacitySelection

TreasureNamePointsWeight

ArtifactsNamePointsCombat

Greeting

Shots

Probability of being friendly.Probability of being indifferent.Probability of being hostile.Normal combat strength.Magical strength.Weight creature may carry.Selection value in initial partycomposition.

Identifying string.Contribution to final tally,Load on carrying creature.

Identifying string.Contribution to final tally.Contribution to combat, ifapplied.Contribution to befriendingstrangers.Number of applications allowed.

Three arrays will hold the generalinformation for creatures, treasure andartifacts respectively. A fourth will holdthe specific information for all creaturesand objects, in three -byte units. The firstof the bytes will indicate the type, referr-ing to an element of one of the arrays,and the others will hold the location andstate. Numbers will be limited by memory

considerations to about 85 entities in all.Combat is resolved in terms of indivi-

dual strengths. If both sides are of thesame size, the opposing creatures arepaired and each individual conflict isresolved independently. If one side is largerthan the other, some of the skirmisheswill be fought two against one.

No more than two creatures may fight asingle creature, except that creatures withmagical power may wield it from behindthe lines, providing that they are not in thefront line themselves.

Artifacts may be brought to bear inparticular quarrels and some mayinfluence the entire battle, applying toeach individual conflict. The total combatpoints applied in any face-off, augmentedby small, random "bonus" points given toeach side, are compared. The side with thehigher number of points wins and one oftheir immediate opponents is killed. Eachgroup in the battle is dealt with this way.

When a party engages in combat with a

group of strangers, the strangers shouldalign to their best advantage. To programthis kind of requirement is usually awk-ward and space -consuming.

Other commands may be given atappropriate points, to accomplish certainoperations. For instance, it may bedesirable to re -distribute the objectcarried by members of the party. TheLUGGAGE command facilitates this. Todetermine totals at the end of a game, theTALLY command is used, although thiswill happen automatically once all theplayers have left the warren.

Certain artifacts have associated com-mands which accomplish special feats. Amagic carpet can FLY the party to anypart of the warren, just once. The magicflute will lull certain creatures to sleep.The code associated with such commandswill first check that the artifact is carriedby a member of the party.'T. J. Radford was a runner-up in ourApple competition.

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AM 'RATING

SIMPLE

WE CONTINUE ourseries of articles on howto program in Basic,probably the most widely -used programminglanguage for smallcomputers.For the series, wehave obtained theserialisation rights forone of the best books onthe subject, IllustratingBasic by Donald Alcock.

*Each month, we arepublishing a part of thebook, so by the end ofthe series you will havethe complete book.It is written with adistinct informality andhas a rather unusualpresentation; but it isthis style, we believe,which makes it one ofthe most easy to readtutorials.

Alcock Illustrating Basic.Chapter 2. c CambridgeUniversity Press.Reprinted by permission.

*Copies of IllustratingBasic can be obtainedfrom PracticalComputing.

PROrtRAMMLIK. LAACMACI

Ua

REFACE

(ii0MPONENTS OF THE LANGUAGE

<8. [INPUT Sr OUTPUT , EXPRESSIONS AND FUNCTIONS

o ctONTROL

C 11APIrER CCAlla 1 NUED

cQ

2

15

39

FOR NEXT Aga. THE CONTROL OF LOOPS 48GO SUB 7 RETURN THE OFtICEPT OF A SUBROUTINE 52MOO fy A GAME. OF BULLS & COWS ILLUSTRATING GO SUB 56

o ,A,RRAYS

,aATRICE5

Ci'caOMPLETE EXAMPLE PROGRAMS

o @OMMANDS AND SIGNING ON

o 7ILE5 OF DATA

YNTAX

59

75

101

111

119

127

JNDE1 132


U-1N

CHAPTER

THIS MAKES BASICOBEY A SEQUENCEOF INSTRUCTIONSAGAIN & AGAIN

WE CALL THIS SEQUENCE A LOOP 0

10 LET M-320 READ X$30 PRINT M;X*40 LET M=M -150 IF M<>0 THEN 2060 PRINT "FEAR TREE"70 DATA "HENS" , "DOVES", "PARTRIDGEgo END

RUN

3 HENS2 DOVES1 PARTRIDGE

PEAR TREE

BUT THE SAMERESULT MAY BEACHIEVED MORESIMPLY AS SHDINHERE IA>.

FORM OF THE

YOU GAN CREATE ALOOP BY SETTINGA "COUNTER"

(I LET 14-3THEM SUCCESSIVELYDEDUCTING i(1, LET M=M -1.;) 9

TESTING THE REMAININGVALUE

1 IF M<>0),AND " LOOPING' BACK

THEN 20UNTIL THE COUNTERRUNS OUTS

10 FOR M = 3 TO 1 STEP -1

i120READ X$

30 PRINT 11;x*40 NEXT M50 PRINT "PEAR TREE"60 DATA 'HENS', 'DOVES' , 'PARTRIDGE'70 END

INSTRUCTION IS

/NSTRuCT/ONS TO BE OBEYED SuccESsivEcy

IF THE STEP IS +1 THEN you MAY SIMPLIFY BY OMITTING" STEP

100 FOR N = P TO Q

LLUSFRATits1 4 BASK PAGE 45

EXPLAINED

LOOPS MAY BE NESTED ONE INSIDE THE OTHER

10

20

40L50

soc70

80

100

110

120

130

140

150

r 160

Tav

170

180f90200210220

PRINT "OLD GLORY (A.D. i912)"FOR R = 1 TO 7LET Pt " "

IF R= 1 THENLET P$= "*FOR C = f TO 8PRINT P$;NEXT CIF R-2.*INT(R/2)=0 THEN 130FOR C.- 1 TO 12PRINTNEXT CPRINTNEXT RFOR R= 1 TO 3FRI-NTFOR C= 1 To 20PRINT "-=";NEXT CPRINTNEXT REND

YOU MAy JUMP OUT OF A LOOP

t OLDE Ene64/311£ FOLKSfONGE "WIDD/COMESE F/1/R'

THIS Is CALLEDSCANNING A LISTTO FIND A MATCH.

cHApi-ER

THERE IS ALWAYSSOME LIMIT TOTHE PERMISSIBLEDEPTH OF NEST-ING . A TYPICALLIMIT IS ABOUT1.0 WHICH ISAMPLE DEPTHFOR EVEN THEMOST COMPLIC-ATED PROGRAM,

LOOPS MUSTNOT BEINTERLEAVED,

10 FOR20 FOR N-

0 NEXT I70 NEXT K

10 REM FIND YOUR PLACE OH THE MARE20 DATA "BREWER", "STEWER" , "GURNEY"30 DATA "DAN/Ey", "WHIDDONK, "iiikwx"40 DATA "COBBLEIGH"50 PRINT "TYPE YOUR. LAST NAME."GO INPUT N$

0 FOR. 1..= 1 To 7Ci80 READ M$90 IF M4>=N$ THEN 130100 NEXT L110 PRINT N4; ' IS NOT ON THE MARE"120 GO TO 140130 PRINT 14; " IS NUMBER"; L140 END

t

THE LOOP/NG VARIABLE Q L ABOVE) KEEPS ITS VALUE IF YOU JUMPOUT OF A LOOP BEFORE THE LOOP HAS RUN ITS COURSE 0 BUT IFYOU DROP OUT AT THE BOTTOM I IN THIS CASE TO LINE 110 )THEN

COW ir _ ASSUME ANYTHING ABOUT THEVALUE OF THE LOOPING VARIABLE

ir MIGHT BE 8 ABOVE THIS ISOVERLEAF) BUT 1r MIGHT NOT . BASICS DIFFER

ILLUSTRATING BASIC PAGE49

U-1N

CHAPTER

THIS MAKES BASICOBEY A SEQUENCEOF INSTRUCTIONSAGAIN & AGAIN

WE CALL THIS SEQUENCE A LOOP 0

10 LET M-320 READ X$30 PRINT M;X*40 LET M=M -150 IF M<>0 THEN 2060 PRINT "FEAR TREE"70 DATA "HENS" , "DOVES", "PARTRIDGEgo END

RUN

3 HENS2 DOVES1 PARTRIDGE

PEAR TREE

BUT THE SAMERESULT MAY BEACHIEVED MORESIMPLY AS SHDINHERE IA>.

FORM OF THE

YOU GAN CREATE ALOOP BY SETTINGA "COUNTER"

(I LET 14-3THEM SUCCESSIVELYDEDUCTING i(1, LET M=M -1.;) 9

TESTING THE REMAININGVALUE

1 IF M<>0),AND " LOOPING' BACK

THEN 20UNTIL THE COUNTERRUNS OUTS

10 FOR M = 3 TO 1 STEP -1

i120READ X$

30 PRINT 11;x*40 NEXT M50 PRINT "PEAR TREE"60 DATA 'HENS', 'DOVES' , 'PARTRIDGE'70 END

INSTRUCTION IS

/NSTRuCT/ONS TO BE OBEYED SuccESsivEcy

IF THE STEP IS +1 THEN you MAY SIMPLIFY BY OMITTING" STEP

100 FOR N = P TO Q

LLUSFRATits1 4 BASK PAGE 45

EXPLAINED

LOOPS MAY BE NESTED ONE INSIDE THE OTHER

10

20

40L50

soc70

80

100

110

120

130

140

150

r 160

Tav

170

180f90200210220

PRINT "OLD GLORY (A.D. i912)"FOR R = 1 TO 7LET Pt " "

IF R= 1 THENLET P$= "*FOR C = f TO 8PRINT P$;NEXT CIF R-2.*INT(R/2)=0 THEN 130FOR C.- 1 TO 12PRINTNEXT CPRINTNEXT RFOR R= 1 TO 3FRI-NTFOR C= 1 To 20PRINT "-=";NEXT CPRINTNEXT REND

YOU MAy JUMP OUT OF A LOOP

t OLDE Ene64/311£ FOLKSfONGE "WIDD/COMESE F/1/R'

THIS Is CALLEDSCANNING A LISTTO FIND A MATCH.

cHApi-ER

THERE IS ALWAYSSOME LIMIT TOTHE PERMISSIBLEDEPTH OF NEST-ING . A TYPICALLIMIT IS ABOUT1.0 WHICH ISAMPLE DEPTHFOR EVEN THEMOST COMPLIC-ATED PROGRAM,

LOOPS MUSTNOT BEINTERLEAVED,

10 FOR20 FOR N-

0 NEXT I70 NEXT K

10 REM FIND YOUR PLACE OH THE MARE20 DATA "BREWER", "STEWER" , "GURNEY"30 DATA "DAN/Ey", "WHIDDONK, "iiikwx"40 DATA "COBBLEIGH"50 PRINT "TYPE YOUR. LAST NAME."GO INPUT N$

0 FOR. 1..= 1 To 7Ci80 READ M$90 IF M4>=N$ THEN 130100 NEXT L110 PRINT N4; ' IS NOT ON THE MARE"120 GO TO 140130 PRINT 14; " IS NUMBER"; L140 END

t

THE LOOP/NG VARIABLE Q L ABOVE) KEEPS ITS VALUE IF YOU JUMPOUT OF A LOOP BEFORE THE LOOP HAS RUN ITS COURSE 0 BUT IFYOU DROP OUT AT THE BOTTOM I IN THIS CASE TO LINE 110 )THEN

COW ir _ ASSUME ANYTHING ABOUT THEVALUE OF THE LOOPING VARIABLE

ir MIGHT BE 8 ABOVE THIS ISOVERLEAF) BUT 1r MIGHT NOT . BASICS DIFFER

ILLUSTRATING BASIC PAGE49

cHAPTER

IOU SHOULD NEVER JUMP INTO THE MIDDLE OF A LaeP:

120 IF A > 2 THEN 210

00210

220230

FOR I = 1 TO 6PRINT ;NEXT ILET A=A -1

BASIC WOULD NOTOBEY A "NEXT"IF IT HAD NOTPREVIOUSLY OBEYEDTHE MATCHING"FOR".

BUT IN MOST BASICS YOU MAY JUMP OUT OF A LOOP AND THENBACK IN AGAIN 1 NOT A VERY GOOD PRACTICE ;)

150 FOR I = 1 TO 6160 READ M$170 IF PIS N$ THEN 300180 NEXT I

300 PRINT M$310 GO TO 180

THE JARGON FOR THISIS A LOOP WITHEXTENDED RANGE

3N GENERAL YOU SHOULD ENTER A LOOP THROUGH ITS "FOR'STATEMENT AND EITHER

FALL THROUGH AT THE "NEXT', OR JUMP OUT AND STAY OUT,

IF YOU NEED EXTENDED RANGE THEN ACHIEVE IT USINGTHE GO SUB" INSTRUCTION DESCRIBED ON PAGE 52.

:IF A PROGRAM IS NOT SUPPOSED TO EXECUTE A LOOP AT ALLUNDER CERTAIN CONDITIONS THEN IT IS SAFEST TO TEST FORTHo5E CONDITIONS, ANDS IF THEY APPLY, TO AVOID THE LOOPALTOGETHER .

102030

FOR I- 1READ C

PRINT C;

TO 5

40 IF C .C 0 THEN BO0 FOR. = 1 TO C. "1155 THE

SO PRINT "*'; LOOP RUNN/rA5

70 NEXT RFROM I TO C

WHEN C50

80 PRINT90 NEXT I100 DATA 3 , 0, -1, 4, 1110 EN

ILLUSTRATING BASIC PA(E 50

RUN

30

-1

***

4 xxxx

THE REASON FOR THISPRECAUTION IS GIVENOPPOSITE.

CHAPTER

LTHOUGH THE CONCEPT SEEMS SIMPLE THERE ARE HIDDENDANGERS WITH LOOPS ; DIFFERENT BAS/CS DEAL WITHTHEM DIFFERENTLY. HERE IS THE INTERPRETATIONIN MORE THAN ONE STANDARD BASIC .

CONSIDER THIS LOOP g

WHERE A,Z & 3 COULD BE.

COMPLICATED EXPRESSIONS Qal,

10 FOR V = A TO z STEP S

40 NEXT V

VHE INTERPRETATION INVOLVES 3 VARIABLES WHICH BASICITSELF CAN USE BUT WHICH YOU a THE USER, CAN NEITHERREFER TO NOR CHANGE CALL THEM dr

MARS VENUS Q. F/SN

LET V=ALET (1= ZLET 9 = S

f

e.y. /I" TWE LOOP

"FOR V = 1 To 3"BECOMES

lY succEssivELy-2,-1, 0THEN 1-1 ON Ex/r

LET (v -Ow), sG1.4( 9)

EXECUTE

S1PDYDOWN TO '"NEXT V"

1'

LET V= V+ 9

'FALLS THROUGH" PAST

NEXT VTHE SOW

EVEN IFHAS

NEVER BEEN EXECUTED.

e.g. FOR V=1 TO 0 STEP +1

gt/r some 8A5ics EXECUTETHE BoDy AT LEAST ONCE

REGARDLESS Or A,Z&S,Y,Veci r E PR E TICIAI OPportrE.

8t'T IN SOME BASICS ITWOULD BE UNDEFINED

VilS LOGIC IMPLIES NO MATTER WHAT CHANGES YOU MAKE TO A,Z, OR sIN THE BODY OF THE LOOP IT WILL NOT AFFECT THE NUMBER OF TIMESROUND THE LOOP. BUT you SHOULD NEVER CHANGE THE VALVE OF VIN THE BODY OF THE LOOP.REMEMBERING THAT MANY BASICS DON'T USE THIS LOGIC , NEVERCHANGE ANYTHING IN THE BODY 7NAT COULD ALTER THE VALUEOf V, A, Z 01 S. KEEP THE CONTROLS 3/14PLE 2

ILLUSTRATING BASIC PAGE 551

cHAPTER

IOU SHOULD NEVER JUMP INTO THE MIDDLE OF A LaeP:

120 IF A > 2 THEN 210

00210

220230

FOR I = 1 TO 6PRINT ;NEXT ILET A=A -1

BASIC WOULD NOTOBEY A "NEXT"IF IT HAD NOTPREVIOUSLY OBEYEDTHE MATCHING"FOR".

BUT IN MOST BASICS YOU MAY JUMP OUT OF A LOOP AND THENBACK IN AGAIN 1 NOT A VERY GOOD PRACTICE ;)

150 FOR I = 1 TO 6160 READ M$170 IF PIS N$ THEN 300180 NEXT I

300 PRINT M$310 GO TO 180

THE JARGON FOR THISIS A LOOP WITHEXTENDED RANGE

3N GENERAL YOU SHOULD ENTER A LOOP THROUGH ITS "FOR'STATEMENT AND EITHER

FALL THROUGH AT THE "NEXT', OR JUMP OUT AND STAY OUT,

IF YOU NEED EXTENDED RANGE THEN ACHIEVE IT USINGTHE GO SUB" INSTRUCTION DESCRIBED ON PAGE 52.

:IF A PROGRAM IS NOT SUPPOSED TO EXECUTE A LOOP AT ALLUNDER CERTAIN CONDITIONS THEN IT IS SAFEST TO TEST FORTHo5E CONDITIONS, ANDS IF THEY APPLY, TO AVOID THE LOOPALTOGETHER .

102030

FOR I- 1READ C

PRINT C;

TO 5

40 IF C .C 0 THEN BO0 FOR. = 1 TO C. "1155 THE

SO PRINT "*'; LOOP RUNN/rA5

70 NEXT RFROM I TO C

WHEN C50

80 PRINT90 NEXT I100 DATA 3 , 0, -1, 4, 1110 EN

ILLUSTRATING BASIC PA(E 50

RUN

30

-1

***

4 xxxx

THE REASON FOR THISPRECAUTION IS GIVENOPPOSITE.

CHAPTER

LTHOUGH THE CONCEPT SEEMS SIMPLE THERE ARE HIDDENDANGERS WITH LOOPS ; DIFFERENT BAS/CS DEAL WITHTHEM DIFFERENTLY. HERE IS THE INTERPRETATIONIN MORE THAN ONE STANDARD BASIC .

CONSIDER THIS LOOP g

WHERE A,Z & 3 COULD BE.

COMPLICATED EXPRESSIONS Qal,

10 FOR V = A TO z STEP S

40 NEXT V

VHE INTERPRETATION INVOLVES 3 VARIABLES WHICH BASICITSELF CAN USE BUT WHICH YOU a THE USER, CAN NEITHERREFER TO NOR CHANGE CALL THEM dr

MARS VENUS Q. F/SN

LET V=ALET (1= ZLET 9 = S

f

e.y. /I" TWE LOOP

"FOR V = 1 To 3"BECOMES

lY succEssivELy-2,-1, 0THEN 1-1 ON Ex/r

LET (v -Ow), sG1.4( 9)

EXECUTE

S1PDYDOWN TO '"NEXT V"

1'

LET V= V+ 9

'FALLS THROUGH" PAST

NEXT VTHE SOW

EVEN IFHAS

NEVER BEEN EXECUTED.

e.g. FOR V=1 TO 0 STEP +1

gt/r some 8A5ics EXECUTETHE BoDy AT LEAST ONCE

REGARDLESS Or A,Z&S,Y,Veci r E PR E TICIAI OPportrE.

8t'T IN SOME BASICS ITWOULD BE UNDEFINED

VilS LOGIC IMPLIES NO MATTER WHAT CHANGES YOU MAKE TO A,Z, OR sIN THE BODY OF THE LOOP IT WILL NOT AFFECT THE NUMBER OF TIMESROUND THE LOOP. BUT you SHOULD NEVER CHANGE THE VALVE OF VIN THE BODY OF THE LOOP.REMEMBERING THAT MANY BASICS DON'T USE THIS LOGIC , NEVERCHANGE ANYTHING IN THE BODY 7NAT COULD ALTER THE VALUEOf V, A, Z 01 S. KEEP THE CONTROLS 3/14PLE 2


V,

CHAPTER

IN MANY PROGRAMS A PARTICULAR SEQUENCE OF INSTRUCTIONSOCCURS SEVERAL TIMES. IN SUCH CASES you DON'T NAVE TOREPRODUCE THAT SEQUENCE SEVERAL TIMES ; YOU MAY PARCEL IT UPAS A SuBROUT/WE AND SIMPLY GO TO THAT Su)3RouTINE FROM ANYLINE IN THE PROGRAM AND RETURN TO THE PLACE. FROM WHENCEYOU CAME.

THE PROGRAM CALLED "OLD GLORY" ON PAGE 49 HAS A SEQUENCE.OCCURRING THREE TIMES

WHICH COULD BE PARCELLED UP AS A UBROUTINE

3e 'r, REM SUBROUTINE WITH B & P4310 FOR I = 1 To B320 PRINT P$;

-- 330 NEXT340 RETURN

AND THE PROGRAM " OLD GLORY" RE -CAST LIKE THIS

10 PRINT "OLD GLORY WITH Go SUB &(-9-20 FOR R = 1 To 7

30 LET P$ = "40 IF R =1 THEN 7050 LET P*--= "*70 LET B=880 GO SUB 30090 IF R -- 2* INT(R/2) =0100 LET B=12110 LET P$=120 Go SUB Boo130 PRINT

-,-140 NEXT.74-150 FOR R.= 1 TO 3

160 PRINT170 LET B= 20180 GO SUB 300200 PRINT210 NEXT R220 GO TO 900

'vas PaSUBROUTINE

THEN 130

RETURN"

ILLUSTRATING BASIC PACE 52

VINE FORM OF THE INSTRUCTION Is :

hbvs NUMBER ONLY:

80 GO SUB 30090

30

NOT AN EXPRESS/ON

.5445RouTINE wiry ONEOR MORE "RETURN" STATEMENTS

SEND/NG CONTROL BACK TO THE LJNEimMEDiArEzy PoLt.owinio "GO SUB"

340 RETURN

CHAPTER t

THIS IS KNOWN

IN THE JARGONAS CALLINGA SUBROUTINE.

NOTE:SUBROUTINES MAYTHEMSELVESCONTAIN "GO SUB"STATEMENTS

" GO SUB" MAY BE ANYWHERE IN THE PROGRAM ; THE SUBROUTINE.BEING CALLED MAY ALSO BE. ANYWHERE / NOT NECESSARILY ONHIGHER -NUMBERED LINES ;;0 . YOU NEED CAREFUL ORGANIZATIONTO PREVENT AN IMPOSSIBLE TANGLE

FEW BASICS ALLOW DUMMY PARAMETERS IN A SUBROUTINE.THEY WORK IN THE MANNER EXPLAINED ON PAGE. 26 IN CONNECTION

WITH DUMMY ARGUMENTS OF FUNCTIONS HERE AGAIN DETAILSVARY A LOT FROM BASIC To EAs/c AND you SHOULDN'T USE

DUMMY PARAMETERS IF YOU WANT "PORTABLE" PROGRAMS .

KE CARE NOT TO "FALL" INTO A SUBROUTINE BY ACCIDENT.NOTICE LINE 9.20 OPPOSITE ; IF THIS WERE OMITTED THERE WOULDBE SUcN A " FALL".

CONTINUED OVERLEAP.


V,

CHAPTER

IN MANY PROGRAMS A PARTICULAR SEQUENCE OF INSTRUCTIONSOCCURS SEVERAL TIMES. IN SUCH CASES you DON'T NAVE TOREPRODUCE THAT SEQUENCE SEVERAL TIMES ; YOU MAY PARCEL IT UPAS A SuBROUT/WE AND SIMPLY GO TO THAT Su)3RouTINE FROM ANYLINE IN THE PROGRAM AND RETURN TO THE PLACE. FROM WHENCEYOU CAME.

THE PROGRAM CALLED "OLD GLORY" ON PAGE 49 HAS A SEQUENCE.OCCURRING THREE TIMES

WHICH COULD BE PARCELLED UP AS A UBROUTINE

3e 'r, REM SUBROUTINE WITH B & P4310 FOR I = 1 To B320 PRINT P$;

-- 330 NEXT340 RETURN

AND THE PROGRAM " OLD GLORY" RE -CAST LIKE THIS

10 PRINT "OLD GLORY WITH Go SUB &(-9-20 FOR R = 1 To 7

30 LET P$ = "40 IF R =1 THEN 7050 LET P*--= "*70 LET B=880 GO SUB 30090 IF R -- 2* INT(R/2) =0100 LET B=12110 LET P$=120 Go SUB Boo130 PRINT

-,-140 NEXT.74-150 FOR R.= 1 TO 3

160 PRINT170 LET B= 20180 GO SUB 300200 PRINT210 NEXT R220 GO TO 900

'vas PaSUBROUTINE

THEN 130

RETURN"

ILLUSTRATING BASIC PACE 52

VINE FORM OF THE INSTRUCTION Is :

hbvs NUMBER ONLY:

80 GO SUB 30090

30

NOT AN EXPRESS/ON

.5445RouTINE wiry ONEOR MORE "RETURN" STATEMENTS

SEND/NG CONTROL BACK TO THE LJNEimMEDiArEzy PoLt.owinio "GO SUB"

340 RETURN

CHAPTER t

THIS IS KNOWN

IN THE JARGONAS CALLINGA SUBROUTINE.

NOTE:SUBROUTINES MAYTHEMSELVESCONTAIN "GO SUB"STATEMENTS

" GO SUB" MAY BE ANYWHERE IN THE PROGRAM ; THE SUBROUTINE.BEING CALLED MAY ALSO BE. ANYWHERE / NOT NECESSARILY ONHIGHER -NUMBERED LINES ;;0 . YOU NEED CAREFUL ORGANIZATIONTO PREVENT AN IMPOSSIBLE TANGLE

FEW BASICS ALLOW DUMMY PARAMETERS IN A SUBROUTINE.THEY WORK IN THE MANNER EXPLAINED ON PAGE. 26 IN CONNECTION

WITH DUMMY ARGUMENTS OF FUNCTIONS HERE AGAIN DETAILSVARY A LOT FROM BASIC To EAs/c AND you SHOULDN'T USE

DUMMY PARAMETERS IF YOU WANT "PORTABLE" PROGRAMS .

KE CARE NOT TO "FALL" INTO A SUBROUTINE BY ACCIDENT.NOTICE LINE 9.20 OPPOSITE ; IF THIS WERE OMITTED THERE WOULDBE SUcN A " FALL".

CONTINUED OVERLEAP.


cHAprER

NOVICES TO PROGRAMMING MAY CARE TO SKIP THISDOUBLE PAGE THE FIRST TIME THROUGH THE. BOOK

"CO SUB" MAY APPEAR ANYWHERE IN A PROGRAM; LIKEWISE THESUBROUTINE BEING CALLED MAY BE ANYWHERE . BASIC HAS

NO SURE. WAY OF ASSOCIATING A " RETURN" WITH THE

PARTICULAR " GO SUB" OF YOUR INTENTION. 4 IT'S NOT LIKE" FOR V= FOLLOWED BY " NEXT V " WHERE THE " V" MAKESTHE ASSOCIATION CLEAR .);) 50 WE DESCRIBE BELOW HOWBASIC IS ABLE TO MAKE SUCH AN ASSOCIATION .

LOWE BASICS DEAL WITH "GO SUB" By A TECHNIQUE. CALLEDSTACK/N6. THE STACK WORKS LIKE THIS ;

WHEN BASIC MEETS "GO SUB" IT NOTES THE.

NUMBER OF THE LINE IMMEDIATELY FOLLOWINGGO SUB" AND PUTS THIS NUMBER ON THE

TOP OF THE STACK : THEN CONTROL GOES TO-THE LINE NOMINATED AFTER "GO SUB"

1

.47HEN BASIC MEETS A "RETURN" IT SIMPLY LOOKS

AT THE NUMBER CURRENTLY AT THE TOP OF THESTACK; GOES STRAIGHT TO THE LINE HAVING THATNUMBER ; THEN THROWS AWAY THAT NUMBER PROMTHE TOP OF THE STACK

HIS LOGIC IMPLIES THAT IF BASIC MEETS A "RETURN" BEFORE THEVERY FIRST " GO SUB " THEN THERE WILL BE AN EMPTY sTAcK,HENCE NOWHERE TO GO iZiry OFTEN A BUG IN THE PROGRAMCAUSING CONTROL TO "FALL" INTO A SUBROUTINE , ON THEOTHER HAND BAS/C MAY KEEP MEETING "GO SUB" BUT NOT

ENOUGH "RETURNS" RESULTING IN THE STACK FILLING TOCAPACITY WHICH VARIES FROM BASIC TO BASIC BUT IS TYPICALLY 10D.

ALTHOUGH NOT ALL BASICS USE THIS PRECISE MECHANISM FORHANDLING "GO SUB" you MAY 771/NA- OF IT THIS WAY WHENTESTING THE PROPOSED LOGIC OF A PROGRAM yoU ARE GOING TOWRITE s WHEN TRACKING DOWN BUGS IN A PROGRAM y AND WHENTRYING TO FIGURE OUT THE LOGIC OF SOMEONE ELSE'S PROGRAM,

HETHER OR NOT YOUR oWN 845/C HANDLES "GO SUB" USING A STACK5 ONLY IMPORTANT IF you WRITE A SUBROUTINE THAT CALLS/T5L-Lf THIS IS KNOWN AS RECURS/ON AND IS ONLY FEASIBLEWITH THE LOGIC OF THE. STACK EXPLAINED ABOVE.

ILLUSTRATING f3Asic PAGE 54

CHAPTER

VINIS STACK SHOWS THAT THE LAST "GO SUB"TO BE OBEYED IS THE SAME AS THE PREVIOUSONE 4.-Z, INDICATING 714AT A SUBROUTINE HASJUST CALLED ITSELF DIRECTLY o EARLIERA SUBROUTINE HAD CALLED ANOTHER WHICH , INTURN, HAD CALLED THE FIRST ONE. AS SHOWNBY THE * ON THE PICTURE. THUS A SUBROUTINEHAD CALLED ITSELF INDIRECTLY.

YOU MAy DISCOVER IF YOUR VERSION OF BASIC ALLOWSSUBROUTINES TO CALL THEMSELVES TRY THE FOLLOWING LITTLEPROGRAM WHICH FINDS THE HIGHEST COMMON FACTOR OF TwoNUMBERS BY EUCLID'S METHOD.

10 PRINT "TYPE 2 POSITIVE INTEGERS"20 INPUT M,N30 GO SUB 7040 PRINT "THEIR H C . F.50 GO 70 140 srors (DOESN'T FALL TNRO

GO REM END OF PROGRAM$uetRoUrINE

IS

70 REM START OF SUBROUTINE80 LET P= N90 LET N<M-N*INT(M/N)100 LET 11 P110 IF N=0 THEN 130120 GO SUB 70130 RETURN140 END

P

YOUR OWN BASICMAy WELL SAYTHERE ARE NOTENOUGH "RETURNS',4:0 IN WHICH CASEIT PROBABLYDOESN'T USETHE LOGIC OFA STACK .((YOU MAy THENCHANGE LINE 120TO "GO TO 70"AND IT SHOULDWORK.)

IF YOUR BASIC ACCEPTS THE PROGRAM WITHOUT ANY ALTERATION TOLINE 120 THEN YOU MAy EXPERIMENT TO FIND THE LIMITING HEIGHTOF THE STACK, THUS IF yoU TYPE 85, 204- THE PROGRAMWILL PRINT THE RESULT WHICH IS 17. BUT IF you TYPE85, 289 THEN THE ALLOWABLE STACKING HEIGHT WILLPROBABLY BE EXCEEDED ALTHOUGH THE ANSWER IS STILL 1.7.

RY " PLAYING COMPUTERS" USING PENCIL PAPER AND POCKETCALCULATOR . THIS SHOULD REVEAL EUCLID'S METHOD AND ALSOSHOW HOW THE STACK BUILDS UP AND COLLAPSES


cHAprER

NOVICES TO PROGRAMMING MAY CARE TO SKIP THISDOUBLE PAGE THE FIRST TIME THROUGH THE. BOOK

"CO SUB" MAY APPEAR ANYWHERE IN A PROGRAM; LIKEWISE THESUBROUTINE BEING CALLED MAY BE ANYWHERE . BASIC HAS

NO SURE. WAY OF ASSOCIATING A " RETURN" WITH THE

PARTICULAR " GO SUB" OF YOUR INTENTION. 4 IT'S NOT LIKE" FOR V= FOLLOWED BY " NEXT V " WHERE THE " V" MAKESTHE ASSOCIATION CLEAR .);) 50 WE DESCRIBE BELOW HOWBASIC IS ABLE TO MAKE SUCH AN ASSOCIATION .

LOWE BASICS DEAL WITH "GO SUB" By A TECHNIQUE. CALLEDSTACK/N6. THE STACK WORKS LIKE THIS ;

WHEN BASIC MEETS "GO SUB" IT NOTES THE.

NUMBER OF THE LINE IMMEDIATELY FOLLOWINGGO SUB" AND PUTS THIS NUMBER ON THE

TOP OF THE STACK : THEN CONTROL GOES TO-THE LINE NOMINATED AFTER "GO SUB"

1

.47HEN BASIC MEETS A "RETURN" IT SIMPLY LOOKS

AT THE NUMBER CURRENTLY AT THE TOP OF THESTACK; GOES STRAIGHT TO THE LINE HAVING THATNUMBER ; THEN THROWS AWAY THAT NUMBER PROMTHE TOP OF THE STACK

HIS LOGIC IMPLIES THAT IF BASIC MEETS A "RETURN" BEFORE THEVERY FIRST " GO SUB " THEN THERE WILL BE AN EMPTY sTAcK,HENCE NOWHERE TO GO iZiry OFTEN A BUG IN THE PROGRAMCAUSING CONTROL TO "FALL" INTO A SUBROUTINE , ON THEOTHER HAND BAS/C MAY KEEP MEETING "GO SUB" BUT NOT

ENOUGH "RETURNS" RESULTING IN THE STACK FILLING TOCAPACITY WHICH VARIES FROM BASIC TO BASIC BUT IS TYPICALLY 10D.

ALTHOUGH NOT ALL BASICS USE THIS PRECISE MECHANISM FORHANDLING "GO SUB" you MAY 771/NA- OF IT THIS WAY WHENTESTING THE PROPOSED LOGIC OF A PROGRAM yoU ARE GOING TOWRITE s WHEN TRACKING DOWN BUGS IN A PROGRAM y AND WHENTRYING TO FIGURE OUT THE LOGIC OF SOMEONE ELSE'S PROGRAM,

HETHER OR NOT YOUR oWN 845/C HANDLES "GO SUB" USING A STACK5 ONLY IMPORTANT IF you WRITE A SUBROUTINE THAT CALLS/T5L-Lf THIS IS KNOWN AS RECURS/ON AND IS ONLY FEASIBLEWITH THE LOGIC OF THE. STACK EXPLAINED ABOVE.

ILLUSTRATING f3Asic PAGE 54

CHAPTER

VINIS STACK SHOWS THAT THE LAST "GO SUB"TO BE OBEYED IS THE SAME AS THE PREVIOUSONE 4.-Z, INDICATING 714AT A SUBROUTINE HASJUST CALLED ITSELF DIRECTLY o EARLIERA SUBROUTINE HAD CALLED ANOTHER WHICH , INTURN, HAD CALLED THE FIRST ONE. AS SHOWNBY THE * ON THE PICTURE. THUS A SUBROUTINEHAD CALLED ITSELF INDIRECTLY.

YOU MAy DISCOVER IF YOUR VERSION OF BASIC ALLOWSSUBROUTINES TO CALL THEMSELVES TRY THE FOLLOWING LITTLEPROGRAM WHICH FINDS THE HIGHEST COMMON FACTOR OF TwoNUMBERS BY EUCLID'S METHOD.

10 PRINT "TYPE 2 POSITIVE INTEGERS"20 INPUT M,N30 GO SUB 7040 PRINT "THEIR H C . F.50 GO 70 140 srors (DOESN'T FALL TNRO

GO REM END OF PROGRAM$uetRoUrINE

IS

70 REM START OF SUBROUTINE80 LET P= N90 LET N<M-N*INT(M/N)100 LET 11 P110 IF N=0 THEN 130120 GO SUB 70130 RETURN140 END

P

YOUR OWN BASICMAy WELL SAYTHERE ARE NOTENOUGH "RETURNS',4:0 IN WHICH CASEIT PROBABLYDOESN'T USETHE LOGIC OFA STACK .((YOU MAy THENCHANGE LINE 120TO "GO TO 70"AND IT SHOULDWORK.)

IF YOUR BASIC ACCEPTS THE PROGRAM WITHOUT ANY ALTERATION TOLINE 120 THEN YOU MAy EXPERIMENT TO FIND THE LIMITING HEIGHTOF THE STACK, THUS IF yoU TYPE 85, 204- THE PROGRAMWILL PRINT THE RESULT WHICH IS 17. BUT IF you TYPE85, 289 THEN THE ALLOWABLE STACKING HEIGHT WILLPROBABLY BE EXCEEDED ALTHOUGH THE ANSWER IS STILL 1.7.

RY " PLAYING COMPUTERS" USING PENCIL PAPER AND POCKETCALCULATOR . THIS SHOULD REVEAL EUCLID'S METHOD AND ALSOSHOW HOW THE STACK BUILDS UP AND COLLAPSES


rn

CHAPTER

THIS IS AN INFURIATING GAME,,

THE PROGRAM SHOWN HERE WAS DESIGNED TOPLAY "A100" AND ILLUSTRATE " GO SUB"

140W TO PLAY

START BY THROWING TWOCAST TYPE ITS SCORE ON

MAKES SURE YOU DoH9TEVERY TIME .)

DICE AS EACH DIE ISTHE KEyBOARD. THIS

PLAY THE SAME GAME

THE COMPUTER CHOOSES A NUMBER WITH FOURDIGITS 4;:k NO TWO ALIKE .;;*

(NOTE: THE

FIRST DIGIT COULD BE ZERO)

YOU GUESS WHAT NUMBER THE COMPUTER HAS

CHOSEN AND TYPE YOUR GUESS WHEN INVITEDTO Do SO,

THE COMPUTER NOTES HOW MANY OF )'OUR DIGITS

ARE RIGHT ;;;i0 BUT IN 77/E WRONG PLACEEACH OF THESE IT CALLS A COW.

THE COMPUTER NOTES HOW MANy of YOUR DIGITSARE NOT ONLY RIGHT BUT ALSO /NRIGHT PLACE ;::# EACH OF THESE IT CALLS ABULL .

HAVING REPORTED YOUR SCORE OF BULLS do COKFTHE COMPUTER INVITES YOU TO GUESS AGAIN

AND SO ON UNTIL you SCORE FOUR BULLSAND NO COWS ,

HERE IS THE PROGRAM:

5 REM THE GAME OF 1400

10 PRINT "THROW TWO DICE"15 INPUT I,

E20 FOR K 0 TO 6*I +J -7

- 25 LET X n RND30 NEXT K35 REM NOW FOR THE

-.-PROGRAM PROPER

ILWSTRINTIN BASic pr,cE 56

11012013o14015016017016019020021022023024025026026510001010

10201030

1040105010601070

10751080

10901100f110112011301140

1150

1160

1200

RUN

LET XINT(1.000 0*RND)LET Y= XGO SUB 1000IF C > o THEN 110 -IREM NO COWS ON COMPARISON WITH SELFPRINT "I HAVE CHOSEN A 4 -DIGIT NUMBERLET T=0LET T=T4-1PRINT "WHAT'S YOURINPUT XGO SUB 1000PRINT B; "BULLS &"; C; COWS"IF B < 4 THEN 180PRINT "THAT WOK" ; T ; "TRIES"PRINTGO 'it 110

REM STOP THIS GAME WITH BREAK' YEYREMLET B=0LET C= 0FOR I =

CHAPTER -1)

GUESS"

SUBROUTINE

1 TOLET = 10+ ILET L = INT (10 *()( -X.r INTWIc.41y4s)FOR J = 1 TO 4 frieeARE EACH DIGIT

IF L<> P THEN 1130

OF r.;_eln/08A..._.,clniarM

LET P = (fo*(y --1,14(INT(Y/M)4-0/14)LET M= 104j

1 14LET C= C+1IF I <>0 THEN 1130LET C a C-1LET B= 15+1NEXT JNEXT IRETURNREMEND

THROW 2. DICE.? 6, 3I HAVE CHOSEN A 4 -DIGIT NUMBERWHAT'S YOUR GUESS? 12340 BULLS & 2 cr,g6

WI4AT'S YOUR GUESS

? 5678AT TOOK G

TAIROqComr,EN5ATE5FOR ROvAIDIN6ERTCRS

Zvi' (3.99999) is 3p.7(3.5'9997 #.1) /5 4


rn

CHAPTER

THIS IS AN INFURIATING GAME,,

THE PROGRAM SHOWN HERE WAS DESIGNED TOPLAY "A100" AND ILLUSTRATE " GO SUB"

140W TO PLAY

START BY THROWING TWOCAST TYPE ITS SCORE ON

MAKES SURE YOU DoH9TEVERY TIME .)

DICE AS EACH DIE ISTHE KEyBOARD. THIS

PLAY THE SAME GAME

THE COMPUTER CHOOSES A NUMBER WITH FOURDIGITS 4;:k NO TWO ALIKE .;;*

(NOTE: THE

FIRST DIGIT COULD BE ZERO)

YOU GUESS WHAT NUMBER THE COMPUTER HAS

CHOSEN AND TYPE YOUR GUESS WHEN INVITEDTO Do SO,

THE COMPUTER NOTES HOW MANY OF )'OUR DIGITS

ARE RIGHT ;;;i0 BUT IN 77/E WRONG PLACEEACH OF THESE IT CALLS A COW.

THE COMPUTER NOTES HOW MANy of YOUR DIGITSARE NOT ONLY RIGHT BUT ALSO /NRIGHT PLACE ;::# EACH OF THESE IT CALLS ABULL .

HAVING REPORTED YOUR SCORE OF BULLS do COKFTHE COMPUTER INVITES YOU TO GUESS AGAIN

AND SO ON UNTIL you SCORE FOUR BULLSAND NO COWS ,

HERE IS THE PROGRAM:

5 REM THE GAME OF 1400

10 PRINT "THROW TWO DICE"15 INPUT I,

E20 FOR K 0 TO 6*I +J -7

- 25 LET X n RND30 NEXT K35 REM NOW FOR THE

-.-PROGRAM PROPER

ILWSTRINTIN BASic pr,cE 56

11012013o14015016017016019020021022023024025026026510001010

10201030

1040105010601070

10751080

10901100f110112011301140

1150

1160

1200

RUN

LET XINT(1.000 0*RND)LET Y= XGO SUB 1000IF C > o THEN 110 -IREM NO COWS ON COMPARISON WITH SELFPRINT "I HAVE CHOSEN A 4 -DIGIT NUMBERLET T=0LET T=T4-1PRINT "WHAT'S YOURINPUT XGO SUB 1000PRINT B; "BULLS &"; C; COWS"IF B < 4 THEN 180PRINT "THAT WOK" ; T ; "TRIES"PRINTGO 'it 110

REM STOP THIS GAME WITH BREAK' YEYREMLET B=0LET C= 0FOR I =

CHAPTER -1)

GUESS"

SUBROUTINE

1 TOLET = 10+ ILET L = INT (10 *()( -X.r INTWIc.41y4s)FOR J = 1 TO 4 frieeARE EACH DIGIT

IF L<> P THEN 1130

OF r.;_eln/08A..._.,clniarM

LET P = (fo*(y --1,14(INT(Y/M)4-0/14)LET M= 104j

1 14LET C= C+1IF I <>0 THEN 1130LET C a C-1LET B= 15+1NEXT JNEXT IRETURNREMEND

THROW 2. DICE.? 6, 3I HAVE CHOSEN A 4 -DIGIT NUMBERWHAT'S YOUR GUESS? 12340 BULLS & 2 cr,g6

WI4AT'S YOUR GUESS

? 5678AT TOOK G

TAIROqComr,EN5ATE5FOR ROvAIDIN6ERTCRS

Zvi' (3.99999) is 3p.7(3.5'9997 #.1) /5 4


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The1979Micro-ComputerShow(incorporating the DIYComputer Fair)

A three day exhibition, withseminars, developed from the highlysuccessful 1978 DIY ComputerShow, giving greater emphasis tothe rapidly expanding area ofPersonal Computers in Business.

Book Now - Save 20%A discount of 20% is offeredon all exhibition space forwhich full payment isreceived before28 FEBRUARY 1979.

This year exhibitors will be able tosell their goods direct from theirstands; creating an ideal marketplace for the ever growing numberof personal computer retail outlets.

For further information write or telephone

Online Conferences Phone: (0895) 39262Cleveland Rd, Uxbridge Telex: 281173England, UB8 2DD Cables: Online Uxbridge

Circle No. 14858

APPLE IITAKES ROOT INSCOTLAND

We are now equipped to deal with your computingrequirements North of the Border.

Think about it-an Apple II is only a local phonecall away.

For your complete system requirements or evenjust a demonstration contact us now andbe ahead of the rest.

GATE MICROSYSTEMS

PITKERRO HOUSEBALDOVIE TOLLDUNDEETEL: (0332) 74390

Circle No. 149

El I I I I I I I I I I I I I I I I I I I I I 11111111111111111111111111111111 I I I I I I I I I I I I I I I I I I I I I 1111111111111111111111111111111 I I I I I I I I IIIIIII

MICROSOLVE

We promise a personal service (H.P. or leasingterms available).

Jllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllh Circle No. 150


--- -If you need advice on which Micro -computer tobuy we can help you. We are specialist's inwriting packages and tailor-made software.Test our medical and sales ledger packages.

Come and have a demonstration on the APPLE IIand the new multi-user, multi -task MICROSTAR45.

11111CROSOLVEMicrosolve Computer Services Limited, 2nd floor125-129 High St, Edgware.Telephone: 01-958-4347.

Tape cassette standards

COST-EFFECTIVENESS is possibly of para-mount consideration when a microcom-puter hobbyist contemplates buying aperipheral bulk -storage device. Mini -floppy diskette is generally too expensiveto consider, being extremely costly, evenin its cheapest versions, being of as littlecapacity as 48Kbytes from a 5fin, disc,compared to as much as 330Kbytes onothers of the same size.

In those circumstances it is not sur-prising that the Philips Compact cassetteis chosen most frequently as the bulk pro-gram dump -and -store device. It still doesnot answer the need for a bulk memorystore on which the user could maintainfiles, address large stores of different pro-grams, or address long loops which areuneconomic for being held within themain computers own limited -capacityRAM. This has been an "if only" situa-tion in the minds of users for some time.

All the cassette -recorders I have seenconnected to computers have so far beenmono machines and have been usedexclusively as program -store -and -dumpdevices. The desire to conform to astandard, a mental block, or sheer tight-fistedness may have caused it to be over-looked that the means of using Compact -cassette bulk -memory have now been withus for some time.

What is proposed is to create an Inter-national Forum to raise a new Standardbased upon the use of a stereo cassette -recorder, using the outer track of eachstereo pair as the store for memory bitsand utilising the inner track as an address-able medium of communication with thecomputer, the tape running at high speedin the search -mode, with the controls setto either FAST FORWARD or FASTREWIND.

When the idea was first conceived somemonths ago, there was little to be found insuitable hardware to support the system,except at high cost. This is now resolvingitself, with much -less -expensive recorderscoming into the market. The manager ofthe TV and audio department of Beattiesdepartment store in Solihull, Birmingham,researched the model numbers ofmachines having either solenoid- or IC -controlled tape functions; some haveremote -control facilities through an exter-nal connector but all could presumably beadapted easily to our purpose.

Ranging in price from £176 to £420, themodels located so far are:-

Technics:RS-671USDRS-678USRS -673RS -M75RS -M85

Sony:TCK 6BTCK 7B IITCK 8BTCK 96R

Pioneer:CT -F 1000

There will no doubt be many more ofthese machines coming into this marketwhere competition is fierce and no-onecan afford to ignore new developments.

Using the outer track for program ormemory and the inner track for address-ing is a system chosen for the desirabilityof keeping the tracks with most 'traffic'

Proposalto replace

Kansas CityStandard

separated, to avoid intermodulation andinter -channel cross -talk; the more pro-tection built into a Standard, the lesstrouble in the future.

The mode of addressing locations onthe inner track which is simplest toorganise is to pre -record a timing trackthroughout the length of the tape. Aspecific area of memory-ROM or RAM-is devoted to the task of increment-ing or decrementing the count along thetiming track for any tape in use, with alltapes beginning from their normal startposition but being addressable in eitherdirection.

The discrepancy in speed betweenFAST FORWARD, FAST REWINDand normal RECORD speed results inany audio signal recorded at normal speed

byBert Martin

being read at the higher speeds as a higherfrequency. Differences between individualmachines must also be taken into account,and this is taken care of by a variable -pitchtone -generator which produces two tonesin constant relationship with each otherthroughout their range.

It is proposed that the scale of thevariable -pitch control should be graduatedin seconds; to use the correct setting itwould be necessary for the operator toperform a simple test on a sample C60cassette.

The cassette is inserted in the recorderat the beginning of a full tape; the time totraverse the whole tape at FAST FOR-WARD speed is then taken, using a watchwith a sweep hand; the time measuredthen becomes the figure selected on thepitch control for all subsequent tapes ofany length, being the setting equivalent tothat pitch which, when recorded at 1 'ipsbecomes the correct pair of pitches to beread by the machine when 'listening' tothe tape on FAST FORWARD or FASTREWIND.

Total time needed to traverse a com-plete C60 cassette from end to end variesbetween roughly 36 and 135 seconds, overa wide range of machinery, requiring anoriginal pair of tones lying between 80and 300Hz for the lower frequency, andbetween 135 and 507Hz for the upper.

These would be transformed into tonesof 2250 and 3800Hz when being read inthe high-speed search mode, these valuesbeing the recommended new standard for

the audio equivalents of 0 and 1 in thebinary numbering scale.

Neither frequency bears a harmonicrelationship to the other, thus allowing awide -band filter in the 'listening' circuit,without any fear of mutual confusion,and ability to accommodate some con-siderable tolerance in the precise fre-quency, either recorded or read.

Cassette access time, when used as bulkstorage, is determined by the relativeposition of the tape, when commanded,and the information location, and willseldom require anywhere near a full tra-verse, but will be a maximum of the timesindicated in the previous paragraph. Thisis slow, when compared to floppies,but is very tolerable in relation to bothprice and total storage capacity.

Capacity is the product of baud -rate x60 seconds x 30 minutes (= one side ofthe tape). Assuming the speed being usedfor information transfer as the fastestcurrently -available system of 2,400 bitsper second, this equates to 4,320,000 bitsper side-that is 540Kbytes. The cassetteused in the system described is thus a1 Megabyte memory device.

Even allowing 20 percent wastage inprogram or memory to gaps betweenblocks of information, plus the spaceneeded for the tape to brake to a stand-still, there is still a capacity of 432Kbytes.

Logic and software control of the sys-tem may well result in less wastage thanthis. Use of shorter tapes, such as theavailable C12 and C15, would often besufficient and would have creditably shortaccess times for a large range of applica-tions, or for specific blocks of infor-mation -retention.

Having expounded the basic architec-ture of the system, its development wouldrequire contributions from a wide range oftalents in computing and electronics, sothat the logic and operating system may bebrought to a standard, and that the interface with bus systems may be designed.

In deference to Kansas City CUTS, weshould choose a new location -name andacronym, and I suggest SolihullSLICEM for its place of origin, and aconvenient meeting centre, and StereoLogic in Cassette External Memory,CUTS and SLICEM both being rathersharp titles.

Anyone wishing to comment further,write to the Editor of Practical Computing.Bert Martin is 46, an avid writer-ofletters, articles, romantic ballads and afirst spy novel-and an electronics enthusi-ast. He picked up the latter interest in theRAF but has spent much of his workinglife in the furniture industry as a worksstudy engineer and works manager. He isnow with the Solihull Area Health Authori-ty. A past secretary of the British Associa-tion of Inventors, he arrived at the Promis-ed Land of Computers only in April, 1978-"since when I cannot stop goggling atevery computer book and magazine I canlay my hands on". co


COMPANY SYSTEM APPLICATION PRICE RANGE

COMARTPO Box 2,St Neots,Cambridgeshire0480 215005

Microbox, Min. size: Chassis with threesockets.Max. size: Chassis with six sockets.

Aimed mainly at OEM industrial users and £704195perhaps the serious hobbyist.Manufactured in Britain by Comart, it willtake Cromemco, North Star and otherprocessors and software.

Cromemco System Two, Min size:Processor alone with six sockets inkit form.Max size: 21 sockets; 512K of memory;up to three mini -diskettes of 90Kbytes each.

Software: Extended Basic; Fortran IV; E395 to aroundCobol; Macro -assembler; Word- £5,000processing, DBMS. American systemsuggested for systems development.

Dynabyte, Memory board for any S100bus system. Available in 16-32K units.

£275-695

Cromemco System Three, Min size:32K memory; terminal and printerinterface; dual 250K -byte IBM compatiblefloppy discs.Max size: 128K memory; two-threeterminals.

Software: Same as System Two. Suitablefor a wide range of commercial andscientific applications. Theoreticalmaximum of 512K of memory.

£4,174-£10,000 -plus

Horizon, Min size: 16K memory; serialinterface; one mini -diskette drive with90K bytes; power supply.Max size: 48K memory; three diskettes;hardware floating point board.

Software: Extended Basic; discoperating system; monitor; access toCP/M range. Manufactured by NorthStar Computers of the U.S. Aimed ateducational and small business users.

£995-£3,500

SOL 20/16, Min size: 16K memory;integral keyboard and monitor; serialand parallel interface; cassette unit.Max size: 64K memory; up to I MB disccapacity.

Software: Extended Basic; Fortran; Focal;Assembler; Editor; Games. AnotherAmerican system from ProcessorTechnology Corp aimed at the smallbusiness and education markets.

£1,78545,000 -plus

COMMODORESYSTEMS DIVISIONLondon NWI01-388 5702

PET, Single unit containingscreen, tape cassette and keyboard.Memory is expandable from 8-32K.

Software: Basic; Games; Businesspackages. The British subsidiary ofCommodore Systems of the U.S. sellsPet for home, educational and smallbusiness applications. Reviewed in theOctober issue of Practical Computing;there are more than 50 dealersthroughout the U.K.

From £695

Kim I, Min size: Processor (6502 chip);small calculator -type keyboard; LEDsix -digit display; built-in interfaces foraudio -cassette and Teletype; 1K RAM;2K ROM.Max size: Can add: Kim 4motherboard; Kim 3B 8K RAM (up to64K); Kim 5 resident assembler.

Software: None available yet, but ithas three good manuals. AnAmerican import which gives Pet -typecapabilities with a maximumconfiguration. For the hobbyist butused mainly as an evaluation board forthe 6502 chip. There are two dealers,GR Electronics and 1 Marshall, which offerfurther facilities.

£1294600 ( VAT)

COMPELEC107 Kilburn Square,Kilburn High Road,London NW601-624 7744

Altair System 1300, Min size: 32Kmemory; dual minifloppy discs, 7IKbytes each formatted; serial interface.Max size: 64K memory; 4 serial ports.

Software: Basic (single and multi-user);Fortran; Cobol. The hardware for theAltair systems is from Pertec in theStates, but the software is Anglo-Dutch.For educational and small business systems.

£3,00045,500

Altair System 70, Min size: 33K memory; Software: Single and multi-user Basic;dual floppy discs, 300K bytes each. Fortran; Cobol; APL. Aimed exclusivelyMax size: 64K memory; provision for at business applications; packages areup to 8 VDUs. available for general and sales and

purchase ledger, payroll, wordprocessing, stock control, estate agency,hotel or small airline reservations,transport management and freight costing.A point -of -sale package will soon be ready.

£4,500 to£10,000 -plus

Altair System 300, Typical size: 64Kmemory; 10MB disc drive; turnkeyprocessor; VDU; Qume daisywheelprinter and disc unit.

Software: Single -user Basic; Fortran;Cobol. The same packages as for theSystem 70 are available for this top -end -of -the -market -business, orientated system.Compelec has its own office inBirmingham, but a full distributornetwork is being set up.

L10,000 -plus

COMPUTERBITS LTD40 Vincent Street,Yeovil,Somerset0935 26522

System 8, Typical size: 64K memory; Software: Basic; Pascal; Fortran. ThisIMB disc storage; serial I/O port for VDU; British -manufactured microcomputerparallel port to printer; CP/M system is almost exclusively for businessoperating system. applications.

£3,00045,000




COMPANY SYSTEM APPLICATIONS PRICE RANGE

COMPUTER MART LTD38 St Faiths Lane,Norwich.0603 615089

VDP-80, Typical size: Single desk -top unithousing a 12 in. display, dual standard floppydisc drive, processor, power units, coolingsystem and fully -programmable keyboardcontaining 62 alphanumeric, 12 numericand 12 cursor controls in separate keypads.Normally sold with 32K memory and I.2Mbytes of disc storage but may be expanded.

Software: Included in the price is asophisticated operating system withCommercial Basic. A range of commercialapplication packages is available, includingword processing if required.

£9,500

COMPUTERWORKSHOP38 Dover Street,LondonW101-491 7507

System I, Typical size: 40K memory;dual 8 in. floppy discs, total storagecapacity I-2MB; Ricoh daisywheel printer.System 2, Typical size: 24K memory;dual minifloppy discs of 80K bytes each;Centronics 779 dot matrix printer; VDU.System 3, 12K memory; cassetteinterface; 40 -column dot matrix printer.

Software: Range of Editors, Assemblers,Basics and Games; Information retrievalpackage. These systems were designedand built in Peterborough and aresuitable for educational, small businessusers and perhaps the more serioushobbyist. There is a large number ofdealers around the country.

System 1-£5,000 -plus; System 2-around £3,000;System 3-from£1,350

EQUINOX COMPUTERSYSTEMS LTD32-35 Featherstone Street,London ECIY 8QX01-253 3781/9837

Horizon, Min size: 16K memory; Z80Aprocessor; single minifloppy disc drive.Max size: 64K memory, threeminifloppy disc drives, any acceptable5100 peripheral boards.

Software: Standard-Basic Interpreter(includes random and sequential access),disc operating system and monitor;Options-Basic Compiler, Fortran, Cobol,and Pilot. The system is suitable forcommercial, educational and scientificapplications. Application software forgeneral commercial users.

£1,000-around £2,500

Equinox 300, Min size: 48K memory;dual floppy discs giving 600K bytes ofstorage; 16 -bit Western Digital m.p.u.Max size: Up to 256K memory; up tofour 10MB hard discs.

Software: Basic, Lisp, Pascal, Macro £5,000-£40,000 -plusAssembler, Text Editor and Processor. Allsoftware is bundled. The system is amulti-user, multi -tasking, time-sharingsystem for 2-12 users. Application softwareis available for general commercial users.

MICRONICSI Station Road,Twickenham,Middlesex01-892 7044

Micros, Typical size: I K monitor;47 -key solid state keyboard; interfacesfor video, cassette, printer and UHF TV;serial I/Os; dual parallel I/O ports;2K RAM; power supply.

Software: Extended Basic; Pascal. A From £400, assembledBritish -designed and manufactured systemwhich is being enhanced rapidly. Alreadyavailable are a 40 -column impact printerusing plain paper at £360; what is claimedto be the cheapest data terminal around-a system with an acoustic coupler and VDUfor £1,020. Prospective applications: smallbusinesses, process controllers and hobbyists. next page)

(continued on

The microcomputer for those whoneed more than the minimum. Theright processor for business,scientific and educational use.Proven applications include Games Educational Word Processing Invoicing Stock Control Sales Ledger Purchase Ledger Mailing Scientific.

THEE

HORIZONThe Horizon computer

includes: -

SpecificationZilog Z80A MPU S-100 bus (12 slots) Solid

well-built case Up to three Shugart mini -floppydisc drives, 90KB each Serial port for CRT orTeletype Real-time clock on motherboard

Optional additionalserial port andparallel port Powerful operatingsystem and monitor

Access to widerange of S-100

special applicationboards.

LanguagesPowerful Basic including sequentialand random access disc files formatted output strings lineeditor machine languageCALL many other facilities. Optional

additional software(under CP/Moperating system)includes BASIC

compiler, FORTRAN and COBOL.Horizon Z80A computer with 24K RAM

and 1 disc drive £1483.2 Disc drives £1823 (exclusive of VAT

and carriage).

Equinox ComputerSystems Ltd,32-35 Featherstone Street.London EClY 8QX.Tel: 01-253 3781/9837.

PRACTICAL COMPUTING February 1979 Circle No. 151

61


COMPANY SYSTEM APPLICATIONS PRICE RANGE

NASCOMMICROCOMPUTERS92 Broad Street,Chesham,Buckinghamshire02405 75151

Nascom I, Min size: CPU; 2K memoryparallel I/O; serial data interface;I K monitor in EPROM.Max size: CPU; 64K memory; up to16 parallel I/O ports.

Software: Mostly games, but a mathspackage is on its way. The British -manufactured system started as ahobbyists' package but has found anincreasing number of industrial users.Printer and minifloppy interfaces are inpreparation. There are about two dozendealers around the country.

From £197.50

NEWBEARCOMPUTING STORE7 Bone Lane,Newbury,Berkshireand

2 Gatley Road,Cheadle,Cheshire0635 49223

Sym I, Size: 6502 chip and keypad, withmemory available in 4K blocks to 64K.

Software: Any Kim software. An American From £200system meant to be the foundation forvery small business and hobbyist users.

7768, Size: CPU board; 4K memory;cassette and VDU interfaces.

Software: Range of Basics and Games. ABritish manufactured system for thehobbyists. Expandable to 64K memory,it is available only in kit form.

Cromemco Z2, Min size: Z2 chassis:power supply; motherboard; CPU; fan;sockets; Byte saver board; I6K memory.Max size: 48-64K memory; dual 8 in.floppy discs.

Software: Basic, Fortran; Assembler;macro assembler. For small business andeducational applications. These systemsare also supplied to more than a dozendealers. Same basic system as Comart.

£1,375 to £4,000

PERSONALCOMPUTERS LTD18-19 Fish Street Hill,London EC301-623 1434

Apple II, Min size: 16K memory; 8KROM; keyboard; monitors; mini -assembler: colourgraphics; Powell card;RF modulator; Games; Paddles andspeaker; 4 demo cassettes.Max size: Expandable to 48K memory, andfloppy discs and printers are now available.

Software: Basic; Assembler; Games;Business packages. An American systemregarded as suitable for any kind ofapplications. There are 15 dealersthroughout the country and maintenancecontracts are offered.

,coo-a,cloo

RAI R30-32 Neat Street,London WC201-836 4663

RAIR Black Box, Min size: 32K memory;dual minifloppy discs, 80K bytes each;two programmable serial I/O interfaces.Max size: 64K memory; 8 serialinterfaces; IMB disc storage (or 10MBhard disc); range of peripherals.

Software: Advanced Basic interpreter,Fortran IV compiler; Cobol compiler.Described by the makers as the only'sensible' British -designed andmanufactured microcomputer, its uses aresmall business and educational applicationsand in distributed processing networks.Hardware distributors are being signedand agreements made with softwarehouses to add software. It is not for thehobbyists. A warranty and U.K.-wideon -site maintenance is given.

E2,300-£8,000

RESEARCH MACHINESLTDPO Box 75,209 Cowley Road,Oxford0865 49793

Research Machines 380Z, Min size: 4Kmemory; 380Z processor; keyboard.Max size: 48K memory.280Z, 4K board plus connecting cables,£398. 32K board-identical inperformance to the 380Z: £722.

Software: Basic interpreter; 12K Basic;Assemblers. A British system usingCP/M software; delivery times are about6 weeks at the moment. A minifloppydisc system is on trial. Sintel is the soledistributor.

From £830

SCIENCE OFCAMBRIDGE6 Kings Parade,Cambridge0223 312919

MK 14, Min size: 8060 SC/MP; fl( usermemory; IK PROM with monitorprogram; Hex keyboard and 8 -digit,seven -segment display; interfacecircuitry; 5v regulator on board.To this can be added: 4-K RAM (£3.60);16 I/0 chip (£7.80); cassette interface kit(E5.95); cassette interface andreplacement monitor (£7.95); PROMprogrammer (£9-95).

Software: None provided, but a 100 -page Basic price is E39-95.manual includes a number which will fit into All prices are256 bytes covering monitors, maths, exclusive of VATelectronics systems, music and miscellaneous.Based on American NationalSemiconductor chips. Science will soon havea VDU interface and large manual on userprogramming. Half of sales are tohobbyists, half to engineers.

STRUMECHENGINEERINGELECTRONICSDIVISION(SEED)Portland Place,Coppice Side,Brown hills,Walsall,Staffordshire05433 4321

MSI 6800, Min size: 16K memory; Act Iterminal (keyboard); cassette interface.Max size: Three disc systems are offered:Minifloppy disc system with triple drives of80 bytes each and 32K memory.Large floppy system with dual312K -byte capacity disc and 32K ofmemory. Hard disc system with 10MB,five fixed, five removable, and 56K.

Software: Basic interpreter andcompiler; super editor assembler; textprocessor on small disc system. This is anAmerican -designed system which is beingincreasingly manufactured in U.K. ASEED survey of its sales showed 60% ofthe customers were educationalestablishments, a further 10% researchinstitutes, 10% hobbyists and the restcommercial companies. A distributornetwork is being set up.

Basic system is 41,100(£815 as kit);Minidisc-E2,500;large floppy disc£3,200; hard disc£8,000 -plus

TANDY CORPORATION TRS-80, Min size: Level I 4K memory;Bilston Road, video monitor; cassette; power supply.Wednesbury, Max size: Level 2 16K memory; lineWest Midlands printer, floppy disc system.021-556 6101

Software: Basic; some business packages.An American system from the 200 -outletTandy chain-The Level I is aimedat the hobbyist and educationmarket and Level 2 at smallbusiness applications.

Level 1-£499;Level 2-£2,434


224 ARTICLESi,mbaud has more articles than any other inicrocomputetmagazme Outing 1977 for instance there were 224 articlesm Koottaud 880 pages of articles Mal 5 like a very large

i won be even .

FOR THE BEGINNERThou,: , - al and Pt09,0a'magside, ,. , written with lirebeg.' ,ner maga,a, makes it as easy touhrt,. 'mowers

THE BEST PROGRAMSOn', rminers both the publication of theirprow, e plus a large royalty for the program itd s issued on cassettes is it any wonder all of the really goodprograms are being published in KilobaucIT You'll find the bestin games. diagnostics. teaching. music. business. etc programsin Kilobaud We're very heavy on programs

HOBBY OR BUSINESS?Both businessmen and hobbyist want the same thing to uncle,stand microcomputers and this is the purpose of KilobaudKB also has articles aimed at the businessman to help himknOw what is available and what it will do

THE PUBLISHERKilobaud is published by the same people who put out 73 Magazine-the largest or the amateur radio magazines

MONTHLY COLUMNSKeep up with the latest developments and readers' programsthrough the tellers column a KIM column one on theTRS-BO a column on BASIC etc The editorials will keep youup to date on moneymaking ideas. the progress of the industry andmore The New Products column is particularly useful. Includingthe results of tests of the latest equipment in the Kilobaud microcoml.., laboratory-the most complete in the industry

SUBSCRIBE TO KILOBAUDYou can get Kilobaud fast. Copies are flown to Europe immediatelyupon publication and mailed directly from the United Kingdom, soyour copies are current. Send subscription orders for UnitedKingdom and Europe. £20 sterling per year. to

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microsense compptersA Division of Data Efficiency Limited

MICROCOMPUTERS FOR BUSINESS & PLEASURE

Professional Dealers RequiredWe are pleased to announce that we have obtained an exclusive agency

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Circle No. 15463

Business Men in the MidlandsThinking of buying a Computer?

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Let us help you through the Maze ?

During 1979 we shall be holding a series of one -day

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Attendance at each seminar limited to 20 people. Individual attention to your problems. Talks by experienced business Consultants. Demonstrations of a full range of working business

software packages. Demonstrations of microcomputers in action. No prior knowledge of computers necessary. Lunch and refreshments available.

To date we have been involved in the installation of morethan 40 small business systems. Why not gain the benefitof our experience? Attendance fee £50.

For further details contact: Mrs D. G. SmithVideo SoftwareStone LaneKinverStourbridgeWest Midlands.

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Circle No. 155

MICRO COMPUTERCOURSES

Seminars on microcomputers.Applications for the computer

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Circle No. 156

zL THE NEWBEAR COMPUTING STORE

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Noughts and crosses

It's not so easy asit might appearmum has been said of chess and othergames but although everyone knowsnoughts and crosses, it has been unfairlyforgotten. Noughts and crosses is notso easy to play as you might think.Making the computer play a watertightgame involves recognising patterns, whichwe have achieved by some algorithms andsome sledge -hammer techniques using IFstatements.

The program is based on a machine -language program written by the authorin 1973 for a Texas 960 minicomputer.Translating to Basic was not easy, asBasic is really not suitable for this kindof work. String matrices are hard to use,since only one result is allowed from anIF statement.

You are 0, the computer is X, and youplay first. A matrix of nine numbers isdisplayed representing the nine squares.You must enter the number of the squaresyou want to enter and the appropriatesquare is changed to a zero. At the sametime the computer's square is changed toan X.

The matrix is displayed again and youthen choose your next square. If you winor lose. suitable messages are displayed.If you draw you get a replay. If you use asquare number which has already beenused you get "CHEAT".

TranslationThe only string variable is S$ which is

used as a status indication which can beprinted. If your Basic does not havestring variables, use different values forOK, WIN, LOSE and then use IF state-ments to print different messages.

ELSE: If your Basic does not have thisfeature you will have to add extra lines,e.g. 391 GOTO 430 deals with line 390.To deal with 400 and 420 move them to401 and 421. At 400 and 420 write P0=8.210 and 430 will need additional IFstatements.

EXIT: This is needed to get out of aFOR loop early without causing a stackerror. Some Basics will allow GOTOinstead, without causing an error. Other-wise if you don't have EXIT you canpush P over the FOR limit then addanother NEXT. For example to deal withline 460 change "EXIT 490" to "GOTO1170". Then at 1170 P =9 :NEXT P:GOTO 490.SPACE: If you run out of it then reducethe dimension of S$, cut down themessages and delete the REMs. Youcould also try deleting one or more ofthe rules, which will increase your chanceof winning. For example, lines 250-280,

or 290-360, or 370-420, or even all of230-440 which will make it very easy towin.

Operation10-50: dimensions the matrix, initialisesthe status word (literally) S$ and puts thevalues 1-9 in the matrix. Note thatelement 0 is not used.80: is where the program loops back oneach play. F is made = 1 when thecomputer blocks a row to prevent anotherentry in lines 210 onwards.100: calls 560 to print the matrix. This istreated as two dimensions V & H andthe contents are printed as they are. 0 isrepresented as 0 and X is represented by-1. Thus lines 600 and 630 print Xwhenever -1 is encountered.110: calls 690 to see if anyone has won.On the first time round no-one has, ofcourse, but on subsequent loops it couldbe the computer.120: If S$ changes its status the gamefinishes.130-160: inputs the user's square, checksit, and enters 0 in the matrix.170-180: the matrix is then re -checkedto see if the user has won.190: calls 860 to check if there is a rowwith only two entries, either of Os (to beblocked) or of Xs (to win) and entersan X in the remaining square.210: If the above tests fail the computertries for the centre square.250-280: biases the computer's moves tothe corners.290-360: checks L -shapes. If the user hasplayed one corner and an opposite sidethen the potential triangle must beblocked.380-420: checks for triangles threatening.430: Implements the decisions made in250-420, if possible. If not then. ...450: Anywhere free will do for the X. Ifthere is nowhere free, the game must haveended in a draw.510: the game ends by displaying thematrix and printing the status.LIST10 DIM M(10),S$(30)20 S$="OK"30 FOR P=0 TO 9/REM INIT MAT40 M(P)=P50 NEXT P60 PRINT "NOUGHTS AND CROSSES. YOU ARE 0,

I AM X"70 PRINT "YOU HAVE FIRST GO: ENTER THE

SQUARE NUMBER YOU WANT"80 F=090 PRINT00 GOSUB 560/REM PRINT MAT10 GOSUB 690/REM TEST LNS OF 3

20 IF S$ < rOK" THEN 52030 INPUT "ENTER SQ: ",PI40 IF M(PI) <I THEN PRINT "CHEAT"50 IF M(PI) <I THEN 54060 M(PI)=070 GOSUB 690/REM RECHK LNS 380 IFS$ < >"OK"THEN 51090 GOSUB 860/REM CHK PRS

200 IF F=I THEN 80

210 IF M(5) >0 THEN M(5)= -I ELSE 240220 GOTO 80230 REM CHECK L SHAPES240 P0=0250 I F (MI)+M(5) <I THEN P0=3260 F M(3)+M(5) <I THEN P0=9270 F M(9)± M(5) <I THEN P0=7280 F M(7)± M(5) <I THEN PO=I290 F M(I)+M(8)=0 THEN P0=7300 F M(I)+M(6)=0 THEN P0=3310 F M(3)+M(4)=0 THEN P0=1320 F M(3)± M(8)=0 THEN P0=9330 F M(9)+ M(2)=0 THEN P0=3340 F M(9)+ M(4)= 0 THEN PO =7350 F M(7)± M(2)=0 THEN PO= I360 F M(7)+ M(6)=0 THEN P0=9370 REM CHECK TRIANGLES FORMING380 F M(I)+M(5)+M(9)=-I THEN 400390 FM(3)+M(5)+M(7)=-I THEN 420 ELSE 430400 F M(I)+M(9)=-I THEN P0=3 ELSE P0=8410 GOTO 430420 F M(3)+M(7)=-I THEN PO= I ELSE P0=8430 F M(P0) >0 THEN M(P0)=-1 ELSE 450440 GOTO 80450 FOR P= I TO 9/REM PUT X ANYWHERE FREE460 IF M(P) >0 THEN EXIT 490470 NEXT P480 PRINT "DRAW"/GOTO 20490 M(P)=-I500 GOTO 80510 GOSUB 560520 PRINT S$530 PRINT "I ENJOYED THAT GAME"540 PRINT "IF YOU WANT ANOTHER GO, TYPE

'RUN"'550 END560 REM PRINT MATRIX570 PRINT TAB(20),580 FOR V=0 TO 2590 FOR H=0 TO 2600 IF M(H+V*3+ I)<0 THEN 630610 PRINT M(H+V*3+1), " ",620 GOTO 640630 PRINT" X ",640 NEXT H650 PRINT/PRINT/PRINT TAB(20),660 NEXT V670 PRINT680 RETURN690 REM CHECK FOR LINES OF 3700 FOR P=1 TO 7 STEP 3710 IP M(P)<>M(P+ I) THEN 730720 IF M(P+1)=M(P+2) THEN EXIT 830730 NEXT P740 FOR P=1 TO 3750 IF M(P)<>M(P+3) THEN 770760 IF M(P+3)=M(P+6) THEN EXIT 830770 NEXT P780 P=5/IF M(P)<>M(P-4) THEN 800790 IF M(P)=M(P+4) THEN 830800 IF M(P)<>M(P-2) THEN 820810 IF M(P)=M(P+2) THEN 830820 P=0/RETURN830 IF M(P)=0 THEN S$"DRAT IT, I'VE LOST!"840 IF M(P)=-I THEN S$="YOU TWIT, I WIN!"850 P=0/RETURN860 REM CHK PAIRS870 FOR P=1 TO 3/REM VERT ROWS880 P0=P+3/IF M(P)=M(P+6) THEN GOSUB 1140890 IF F= I THEN EXIT 950900 PO=P/IF M(P+3)=M(P+6) THEN GOSUB 1140910 IF F=1 THEN EXIT 950920 P0=P+6/IF M(P)=M(P+3) THEN GOSUB 1140930 IF F= I THEN EXIT 950940 NEXT P950 IF F=I THEN RETURN960 FOR P= I TO 7 STEP 3/REM HORIZ970 PO=P+ I/IF M(P)=M(P+2) THEN GOSUB 1140980 IF F-1 THEN EXIT 1040990 PO=P/IF M(P+I)=M(P+2) THEN GOSUB 1140000 IF F=1 THEN EXIT 1040010 PO=P+2/IF M(P)=M(P+ I) THEN GOSUB 1140020 IF F=1 THEN EXIT 1040030 NEXT P040 IF F=1 THEN RETURN050 FOR P=2 TO 4 STEP 2/REM DIAGONALS060 P0=5/1F M(5 +P)=M(5-P) THEN GOSUB 1140070 IF F=I THEN EXIT 1130080 P0=5+P/IF M(5)=M(5-P) THEN GOSUB 1140090 IF F=1 THEN EXIT 1130100 P0=5-P/IF M(5)=M(5+P) THEN GOSUB 1140110 IF F=1 THEN EXIT 1130120 NEXT P130 RETURN140 IF M(P0)<1 THEN RETURN150 M(P0)=-1160 F= I/RETURN

READYWritten in North Star Basic by D. N.Sands and staff at Sands -Whiteley Re-search & Development Ltd., microcom-puter consultants, Royston, Herts. 113


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TWIN CASSETTE INTERFACE RAM - 1K TO 4K OPTIONSOPTIONS INCLUDE:8K BASIC INTERPRETER ROM4K ASSEMBLER/EDITOR ROMAIM 65 comes to you fully builttested with a full alphanumerickeyboard. 20 character display and a20 column printer - for keeping apermanent record of all your work.Available in 1K- and 4K -byte RAMversions, AIM 65 is designed around the6502 CPU, which has 64K addresscapability with 13 addressing modesThis is the microprocessor at the heartof many other, more costly, systemssuch as PET and APPLE.AIM 65 has a 4K ROM -resident monitorprogram for all peripheral control anduser programming functions.Spare sockets are included forexpanding on -board program memoryvia user PROM -based programs and/orRockwell assembler, text editor andBASIC interpreter plug-in optionsAIM 65 has a connector for externalaccess to system bus for memory and110 expansion. a separate connector

for interfacing a teletype and twocassette recorders. There is a user -dedicated Versatile Interface Adaptor,featuring three 8 -bit. bidirectional ports(two parallel, one serial) and two 16-bilinterval timer/event counters - thusallowing Ithe I user to interface his ownsystem, without extra interface devicesin many cases.AIM 65 is probably the most effective,tow -cost microcomputer developmentsystem available - an invaluableeducational aid to first time users andand ideal general purpose micro-computer for the engineer.AIM 65 is available in the UK only fromPELCO ELECTRONICS LTD at £249.50+ VAT, complete with User's Manualand Schematic, R6500 Programmingand Hardware Manuals and a handynocket reference card

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66


Computabits

Moving softwarefrom one microto anotherMark Witkowski looks at how to overcome the difficulty of movingsoftware written for one make of computer to another. The mainmethod of attacking this problem is to disassemble and relocate theprogram so that it fits on to your own computer.In this and next month's issue he will describe how to tackle thistask, which is not as difficult as it may seem, and which is applicablenot only for the 6800.

DISASSEMBLERS are a most useful soft-ware tool for microprocessors. A gooddeal of software available on the currentrange of micros is supplied only in objectform. If the original code was written inassembly language, the program sourcelisting will probably be too bulky to besupplied.

Not providing a listing also protects theauthor's effort in programming. If theuser's set-up is not identical to thatavailable to the author, however, substan-tial changes may be called for if the pro-gram is to run satisfactorily. A typicalinstance might be that the user's systemhas read -only -memory -based code atlocations which contained randomaccess memory when the program wasdevised.

Different monitors will assume differ-ent stack locations and monitor routineswill be at different addresses. Most pro-grams use at least the monitor transportroutines. Any of those things will preventthe program running properly.

Correcting these deficiencies involvesunderstanding how the program worksand then altering the code. When high-level languages become common onmicroprocessors, even if the programlisting is supplied, there will still be timeswhen understanding what is happening atthe machine level is essential.

Simple processPlodding through a hexidecimal dump

constitutes an almost impossible task. Inany case, it is far more difficult than itneed be. A disassembler, and there aremany available, will translate the hexnumber into the original mnemonic formof the assembly language. For example,"E7" becomes "STAB" or "54" to"LSRB", which is of far more value.

The process is a simple one. In theMotorola M6800 instruction set, each ofthe 256 possible instructions either mapson to a mnemonic or is totally unused.By setting -up a table of such 'words' andthen using the corresponding numericvalue of the instruction as a key to select


the correct one, it is a trivial matter toprint the instructions in the helpfulmnemonic form.

The disassembler discussed here iscoded in the Basic programming language.There are numerous disadvantages tousing Basic for disassembly, compared towriting it directly in assembly code. Theprogram is much larger, the residentinterpreter is required, the whole takingnearly 16K bytes. A hand -coded versionwould only take about 1.5K.

More than necessaryBasic uses all the resources inefficiently.

The program is stored in random accessmemory as literal lines or text. The list ofmnemonics is stored as 255 string varia-bles in an array. SWTP Basic fixes thestring variable storage length at 18characters, even though the program usesonly the first five in each string, at most.Therefore the mnemonic table alone uses4,596 bytes, about 3,500 more than itneeds.

If space were at an absolute premium,the mnemonics could be packed three to astring but the code would be made morecomplex as a result. Further, the mnemon-ics are stored twice, once in the sourceprogram in DATA statements and againin the string variables.

Considering the trouble involved ininputting the table for each run of theprogram, I am content to leave the DATAstatements. Basic also executes code veryslowly. There must be a factor of severalhundred in run-time speed for the Basicover well -written assembly code for thisapplication. This is not surprising whenone considers that the interpreter mustlook at each character in the sourcebefore doing anything, and that thearithmetic is done on numbers accurate to10 places.

Worse than these, which are badenough, the Basic interpreter and programsit between locations zero and 16K-justwhere most programs to be disassembledwill be themselves. One could use the


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67

PETSales &Service?We've got you covered ... with aunique Nationwide network ofPET -orientated dealers offering:* PET SALES* PET SERVICEmany maintenance agreementsalready in force* PET SOFTWARE* FULL RANGE OF PETperipherals including the TeletypeM43 printer.For instant attention from thePET SPECIALISTS ring:SCOTLAND041-776-4388Robox Office Equipment Ltd,84 Townhead,Kirkintilloch, GlasgowNORTH0632-774540Currie & Maughan Systems,204 Durham Road,Gateshead,Tyne & WearMANCHESTER EtNORTH WESTPlease enquire in the firstinstance to: -01 -254 9293C.S.S. (Business Equipment) Ltd,502 Kingsland Road,London E8 4AEMIDLANDS0602 206647A.J.R. Office Equipment Services,5 Church Drive,Daybrook,NottinghamBRISTOL0272-651449C.S.S. (Bristol) Ltd,351 Fishponds Road,Bristol BS5 6RTLONDON Et HOMECOUNTIES01-254-9293C.S.S. (Business Equipment) Ltd,502 Kingsland Road,London, E8 4AECBM APPOINTEDGOVERNMENTDEALERS

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i8


disassembler to re -locate the Basic some-where else in memory. In fact, the dualconsiderations of patching the Basic towork on our system, and the possible needto re -locate it, provided most of theimpetus to do this work. It was also some-thing of a challenge to write a program inBasic to disassemble itself.

On the advantage side, the single factthat this program, written in a high-levellanguage, is so much easier to write,debug and describe goes all the way incounter -balancing the disadvantages.Those are among the reasons given mostoften for using high-level languages.

In time- or space -sensitive applicationsthe algorithm-which is generally lan-guage-independent-may be tried andtested using the high-level languages andthen be re -coded carefully, possibly witha slight overall reduction in the time ittakes to go from the initial idea to the useof the final printout, rather than going`from cold' directly in assembler.

This route certainly gives a greaterunderstanding of the problem and itssolution. Whenever a program is used andthen re -coded in this way, minor, andsometimes major improvements becomeapparent and are incorporated in the finalprogram.

The problem with which we are faced isto take an apparently arbitrary collectionof binary digits and restore them to areadable form. How can a hexidecimalstring such as "9F0D207A8D" and thelike be presented in a usable way? Eachmanufacturer produces, with every pro-cessor family, an assembly language for-mat. Motorola is no exception. Eachinstruction to the microcomputer toperform an action is given a mnemonic.

Clearly relatedThis is related clearly to the English

description of the action. Thus, Storethe current contents of the A -accumulatorinto the location pointed to by the con-tents of the stack pointer, and then decre-ment the contents of the stack pointerregister by one" maps first to "PSHA"and then to the hex "36".

It would not be impossible to devise aprogram thus to expand machine code.The result would be extremely verboseand ultimately, therefore, about as muchuse as the binary. Mnemonics-literallyan "aid to memory"-provide a usefulcompromise. Because these mnemonicsmap so closely to the actual machine codethe programmer has a considerable degreeof control over the processor. In assemblylanguage an instruction is written in theform: label, separator, operator (mne-monic), separator, operand, separator,comment. In most cases the separator isone or more spaces. So:

NEXT IMP BACKmeans 'this instruction is called NEXT, ifit executed jump (transfer control) to theinstruction called BACK'. For those

machine instructions with an operand,and some which do not, it is stored in theone or two bytes following the instruc-tion byte.

There are 72 mnemonics and 172instructions for the M6800. This disparityis accounted for by each mnemonic beingused in a number of modes. Motoroladescribes seven modes-inherent, relative,immediate, extended, direct, indexed andaccumulator. For a full description of themodes, the M6800 Microprocessor Pro-gramming Manual should be consulted.

Briefly, inherent mode is a single -byteinstruction and therefore has no operand.They will be used to affect the internalregisters. The next instruction is found inthe next byte.

Relative mode will be used to transfercontrol if some specific bit pattern exists inthe condition codes. The operand is asingle -byte signed number, which is addedto the current program location to deter-mine the next instruction to be executed.If the required bit pattern is not present inthe condition code register, two is addedto the program counter and the programcontinues with the next instruction. Inboth inherent and relative mode instruc-tions there is only one mode for eachmnemonic.

Immediate modeWith immediate mode instructions the

operand, always an expression which canbe reduced to a single number, is placed inthe next byte(s) and will be used as aconstant. "ADDA #3" adds three to theA -accumulator. Immediate mode isindicated in the assembly language bypreceding the operand by the " f "character.

With direct mode, the operand willspecify the address of the machine loca-tion in which the number to be used willbe found. "ADDA 3" means add thenumber stored in address "three' to theA -accumulator. The operand is stored inone byte and therefore the range ofaddresses to manipulate the data is limitedto the first 256 bytes of the microprocessoraddress space. Extended mode allows atwo -byte operand and so the addressspecified to contain the data can be any-where in the 65536 -byte address space.

Indexed mode provides a 16 -bit wideindex -register, the X -register, whose con-tents will specify the location at which thedata is to be found. The one -byte operandconsists of an unsigned binary numberwhich will be added to the X -register be-fore it is used to retrieve or store the data.This mode is denoted in the assemblylanguage by placing the characters ",X"directly after the operand.

Accumulator mode will specify whichof the two accumulators, A or B, will beaffected by a particular operation. In thelanguage "A" or "B" may be placeddirectly after the operator field.

Subtract ("SUB") is an example of an(continued on next page)



instruction using many modes. This singlemnemonic maps to eight machine codevalues, according to its mode:

SUBA *3 to 8003SUBA 10 to 900ASUBA 0,X to A000SUBA $2000 to 802000

for the A -register mode, and:SUBB *3 to C003SUBB $10 tp D010SUBB 0,X to E000SUBB 2000 to F007D0

for the B -accumulator.

(immediate)(direct)(indexed)(extended)

(immediate)(direct)(indexed)(extended)

The task for the disassembler is to takethe hex digits shown on the right, and toproduce the text shown on the left. Forthis program the method chosen is tostore the relevant mnemonic for each ofthe 256 possibilities and then to use thenumeric value as the subscript for thecorrect string array element.

Careful analysis of the operator valuesshows that each mnemonic is classedtogether according to the binary value ofthe operand. Thus for "SUB" bit 7 isalways set, bit 0,1,2 and 3 are alwaysunset and bits 5,6 and 7 carry the modeinformation (1XXX0000). The trade-off between the amount of code requiredto extract the mnemonic in this wayscarcely justifies the storage gains.

Stored with each mnemonic in the datastring is a digit which describes theaddressing mode of the instruction. Theseare not identical to the ones described byMotorola, but are related closely.Inherent "2", immediate "3", direct "4",extended "5", relative "6" and indexed"7" remain the same. Accumulator modeis dispensed with, because they areexplicitly mentioned in the stored string.

New modeA new mode, extended immediate "8",

is added to cater for three instructionswhich do not follow the usual immediatemode rule of a single -byte operand."CPX I ", "LDX # " and "LDS *" allload or compare the 16 -bit index andstack registers with a two -byte operand.Even when writing assemblers they have tobe tested-for individuality and it seemsstrange that Motorola admits to theirbeing different.

Undefined operator values are giventhe mode "1" and will cause the dis-assembler to print a "*NO INSTRUC-TION" message. This should not beconfused with the inherent "NOP" (nooperation) instruction, which has theeffect of moving program control to thenext byte. Taking two machine cycles inthe process, 'No Instruction' will causethe processor to cease computing, almostalways requiring a re -set before it willcontinue. If such a byte is encounteredwhile disassembling code, then it hasgone past the end of the program, or hasrun into the program data areas.

The disassembler, after it has read themnemonic table into the string arrayQ$, begins by requesting a 'Start Address'.It uses this to extract the contents of thatmachine location with the Basic system


Computabits

function "PEEK", (st. 640). The valuereturned is used to pick one of themnemonics (st. 670) and its mode (st. 660)from the table. If that location containedzero (st. 650) it is a 'No Instruction',otherwise the mode (in variable A)transfers control to one of the eight codeblocks with a computed goto (st. 680).

`No Instruction' mode (st. 1100 to1110) prints a message, followed by arequest for a new start location (st. 300).For the remaining seven modes theinstructions are printed in a style as closeto the original assembly code as possible.The label is replaced by the actualaddress of the instruction. Then theoperator mnemonic is printed.

With the exception of inherent mode(st. 1200 to 1215), which has no operand,the operand field is printed next. Forimmediate mode (st. 1300 to 1355) a "*"is printed before the one -byte operandvalue. If the operand is between 32 and125 it could be interpreted as a printingASCII character.

In assembly notation an immediateASCII character is denoted by precedingit with the string " ". This is placed inthe comment field, as a useful guide(st. 1345). For direct (st. 1400 to 1435)and extended (st. 1500 to 1540) modes theoperand is printed as a one- or two -bytenumber directly.

For relative mode (st. 1600 to 1645) thevalue of the operand is calculated fromthe current program location and theoffset stored in the second byte. Signedarithmetic, available on the M6800, has tobe simulated in Basic by statements 1610and 1615. The operand is then the actualaddress to which control will transfer.

After the operand in indexed mode(st. 1700 to 1735) the string ",X" isprinted. Extended immediate mode (st.1800 to 1835) is like ordinary immediatemode but with a double -byte operand.Printing the ASCII character equivalent isalso meaningless then, so that code isomitted.

The program counter (P1) is alwaysincremented by the correct amountbefore the control jumps back to statement.440 and the next instruction is tackled.All numbers are printed in hexidecimal.Since the PEEK function returns adecimal number, a subroutine to convertdecimal to hex had to be written, subrou-tine 4000. This routine will cater for bothone- and two -byte numbers, provided thenumber is in the correct range.

DivisionThe number is divided by 4,096, or 256

if it is one byte. The quotient is in therange zero to 15 and is converted to anASCII character digit by statements 4080to 4110 if it is between zero and nine. Tento 15 get converted to "A" to "F" bystatements 4120 to 4150. If the originalnumber is too large this quotient will be16 or greater, the output string (D$) will


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be loaded with four exclamation marks,to denote a number format error.

Having thus determined the first digitthe remainder is extracted and multipliedby the divisor (st. 4190), to give aninteger remainder. The divisor is thendivided by 16, so 4,096 becomes 256; 256becomes 16; and 16 becomes 1, to extractthe remaining digits, which are successive-ly concatenated to the string D$ as theyare produced. After the final stage thisstring contains the answer.

By starting at 4000, and a divisor of 16,two -digit hex numbers are formed. Bystarting at 4040, a divisor of 4,096, four -digit numbers are obtained.

To maintain consistency with theassembly language, a dollars symbol isplaced before each hexidecimal number inthe operand. If the user prefers to work indecimal, each call of GOSUB 4000 or 4040could be replaced by D$-STR$(P6), inwhich case the dollar symbol should bedispensed with. Should octal be yourpreferred number base, R1 will be set to512 for one -byte and 32768 for two -bytenumbers. Division by 8, not 16, is calledfor at statement 4200. Also the dollarprefix should be replaced by the 'commer-cial at' sign "@" to denote an octalnumber.

ConversionSubroutine 5000 converts a hexideci-

mal number stored in H$ into a decimal inPI, making the input of the start addresseasier. Each digit is taken in turn, con-verted by the ASC system function (st.5040) and statements 5050 to 5080 if "0"to "9" and 5090 to 5120 if "A" to "F"into a decimal number between 0 and 15.This is then added to a running total,which is multiplied by 16 prior to eachaddition. So, OAEF is 0 x 4096 + A x256 + E x 16 + F x 1.

Figure 1 shows a portion of the dis-assembled listing. The first start address isthat of the whole program. It is not verylong before a 'No Instruction' is reached.Since the program must continue on an

Figure I : Portion of disassemblyRUN

* START ADDRESS (HEX)? 1000100 JSR $OAEF0103 JMP $0509+ NO INSTRUCTION

START ADDRESS (HEX)? OAEFOAEF LDX #501309OAF2 STX $A000OAFS STX $A006OAFS BSR $OAD3OAFA LDAA # $00OAFC STAA $96OAFE LDAA #$40 4tOBOO STAA $920B02 LDAA * $30 4,0OB04 STAA $93OB06 JMP $0BA5OB09 LDAA # $000808 STAA $96OBOD LDX * $80000810 LDAB =$13OBI2 LDAA $11OBI4 STAB $00,XOB16 STAA $00,XOBIS LDX #$8008OB I B STAB $00,XOB I D STAA $00,XOB I F LDX $800COB22 STAB $00,XOB24 STAA $00,X0826 LDAB #$04

instruction, the new start address can bechosen from the operand of any programcontrol change statement, JMP, JSR, orany branch instruction.

Each output line takes about threeseconds to compute, not including theprintout time. This is mainly due to theslow speed of the decimal to hex conver-sion routine. Figure 1 shows how usefulthis technique can be for understanding anobject loaded program.

Compare this to figure 2, which is alisting produced by the 'T' command of

Figure 2: Hex notation using 'T' commandof same area of memory as Figure I

*T 0100 01060100 BD OAEF0103 7E OB09

*T OAEF 0894OAEF CE 0809OAF2 FF A000OAFS FF A006OAFS 8D D9OAFA 86 00OAFC 97 96OAFE 86 400800 97 920802 86 30OB04 97 93OB06 7E OBA5OB09 86 00OBOB 97 96OBOD CE 8000OBIO C6 13

01312 86 II0B14 E7 00OB16 A7 00OBI8 CE 8008OBIB E7 00OB ID A7 00OB I F CE 800C0822 E7 00OB24 A7 00OB26 C6 04

the MSI monitor. This lists bytes inmemory in instruction/operand format.The choice between a one-, two- or three -byte instruction is achieved in the MSImonitor with a miserly 28 bytes of pro-gram code, not including the commandinterpreter and print routines.

Figure 1 is still far from what isrequired. It would be much better if thelisting produced by the disassemblerre -constituted all four fields, the label aswell. Further, it should need only a singlestart address, deciding automaticallyfrom where to continue disassembling.While it was about it, it could say wheredata locations were, and how many byteswere reserved.

By taking careful note of the values ofthe operands for particular modes ofinstructions, this is all possible. In parttwo techniques for full disassembly willbe discussed. If a statement had a labeloriginally, one is present on the listing. Ifnot, this optional field is left blank. If alocation was declared as data, then data isreserved. The aim is to produce a listingwhich could be fed directly back into anassembler, re -located if necessary.

LIST 99,6800099 DATA "2NOP ",2NOP , I, I, "I"0100 DATA "2TAP ",2TPA ,21 NX ,2DEX ,2CLV

DATA,"2CLC "

0101 "2SEC ",2CLI ,2SEI ,2SBA ,2CBA , 1, I, I,I, "2TAB "

0102 DATA "2TBA ", I, 2DAA , I,2ABA , I, I, I,I,6BRA, 1,613HI , 6BLS , "6BBC"

0103 DATA "6BCS ",6BNE ,6BEQ ,6BVC ,6BVS,6BPL ,6BMI,6BGE , "68LT "

0104 DATA "6BGT ",6BLE ,2TSX , 2INS ,2PULA,2PULB, 2DES ,2TXS , "2PSHA"



(continued from previous page)0105 DATA "2PSHB", I, 2RTS , 1,2RTI , I, 1,2VVAI

,"2SVV1"0106 DATA "2NEGA", I, 1,2COMA, 2LSRA, I, 2RORA,

2ASRA, 2ASLA, SROLA, "2DECA"0107 DATA "I",2INCA, 2TSTA, I,2CLRA, 2NEGB,

I, I, 2COMB, "2LSRB"0108 DATA "I",2RORB, 2ASRB, 2ASLB, 2ROLB,

2DECB, I, 2INCB, ST2TB, "I"0109 DATA "2CLRB", 7NEG , I, I, 7COM , 7LSR , I,

7ROR , 7ASR , 7ASL , "7ROL "0110 DATA "7DEC ", I, 7I NC , 7TST , 71 MP , 7CLR

,5NEG I, I, 5COM , "SLSR "0111 DATA "I", 5ROR ,5ASR ,5ASL ,SROL ,5DEC

DATA,5TST ,"5JMP "

0112 "5CLR ",3SUBA, 3CMPA,3SBCA,I,3ANDA, 3BITA, 3LDAA," I"

0113 DATA "3EORA", 3ADCA, 3ORAA, 3ADDA,8CPX ,6BSR ,8LDS , I,"4SU8A "

0114 DATA "4CMPA",4SBCA, 1,4ANDA,4B I TA,4LDAA, 4STAA, 4EORA,"4ADCA "

0115 DATA "4ORAA", 4ADDA, 4CPX , I,4LDS,4STS ,7SUBA,7CMPA, "7SBCA"

0116 DATA "I", 7ANDA, 78 ITA, 7LDAA, 7STAA,7EORA, 7ADCA, 7ORAA, "7ADDA"

0117 DATA "7CPX ", 7JSR ,7LDS ,7STS ,SSUBA,SCMPA, SSBCA, "I"

0118 DATA "5ANDA", 5BITA, 5LDAA, SSTAA,SEORA, 5ADCA, 5ORAA, "SADDA"

0119 DATA "8CPX ",SJSR ,SLDS ,SSTS ,3SUBB,3CMPB, 3SBCB, "I"

0120 DATA "3ANDB", 3BITB, 3LDAB, I, 3EORB,3ADCB, 3ORAB, "3ADDB"

0121 DATA "I", I,8LDX , I,4SUBB, 4CMPB, 4SBCB,I, 4ANDB, 4BITB, "4LDAB"

0122 DATA "4STAB", 4EORB, 4ADCB,4ORAB,4ADDB, I, I, 4LDX, "4STX "

0123 DATA "7SUBB", 7CMPB, 7SBCB, I, 7ANDB,7BITB, 7LDAB, "7STAB"

0124 DATA "7EORB", 7ADCB, 7ORAB, 7ADDB, I,I, 7LDX , 7STX , "7SUBB"

0125 DATA "SCMPB", 5SBCB, I, SANDS, 5BITB,5LDAB, 5STAB, 5EORB,"5ADCB"

0126 DATA "SORAB", 5ADDB, I, I, SLDX , "SSTX "0190 RESTORE0200 DIM (Q£(255)0220 FOR M9=1 TO 2550230 READ QE(M9)0240 NEXT M90300 INPUT "* START ADDRESS (HEX)", 1-1£0310 GOSUB 50000320 IF PI <65537 THEN 4400330 PRINT "* INCORRECT NUMBER FORMAT"0340 GOTO 3000440 P6 =P I0450 GOSUB 40400460 LE=DL+"0640 I I =PEEK(P 1 )0650 IF II =0 THEN 11000660 A=VAL(LEFTE(QE(11),0670 OC=RIGHTC Q£(11), 4)0680 ON A GOTO 1100, 1200, 1300, 1400, 1500, 1600,

1700, 1800

READY

LIST 1000, 1835100 PRINT "* NO INSTRUCTION"110 GCTO 300200 REM INHERENT MODE205 PRINT LC;Oi210 PI=PI+I215 GOTO 440300 REM IMMEDIATE MODE305 12=PEEK(P1 I)310 PI=P1+2315 P6=12320 GOSUB 4000330 PRINT LE;0£;" *$";Dr;335 IF I2<32 THEN 1350340 IF 12)127 THEN 1350345 PRINT " *' ";CHRf(12);350 PRINT " "355 GOTO 440400 REM DIRECT MODE405 12=PEEK(P1 I)410 PI=PI 2

Computabitsom415 M3 -1420 P6=I2425 GOSUB 4000430 PRINT LL;OL;" $";DE435 GOTO 440500 REM EXTENDED MODE505 12 = (PEEK(PI + I )*256)+ PEEK(P I 2)510 P1=P1+3511 M3=1515 IFI1=126 M3=2520 IF II -=189 M3=3525 P6=12530 GOSUB 4040535 PRINT 11;0£;" $";DL540 GOTO 440600 REM RELATIVE MODE605 12=PEEK(P1+ I)610 IF 12(128 P6=12+2+PI615 IF 12)=128 P6=PI-254 { 12

620 M3=2625 IF11-141 M3=3630 GOSUB 4040635 PRINT 11;0£;" $";D£640 PI=PI +2645 GOTO 440700 REM INDEXED MODE705 12=PEEK(P1+706 P6=12708 GOSUB 4000

710 PRINT Li;OL:"S";D1;",X";715 IF11-110PRINT" !IDXD .IMP";720 IF 11=173 PRINT" IIDXD JSR";725 PRINT " "730 PI=P1+2735 GOTO 440800 REM EXTENDED IMMEDIATE MODE805 12-(PEEK(PI +1)*256)+PEEK(P1-4 2)810 M3= I815 P6= 12820 GOSUB 4040825 PRINT L£;01;" *$";DL830 P 1 -= PI 3

835 GOTO 440READYLIST 4000, 60004000 REM PRINT NUMBER IN P6 IN HEX (0-255)4100 RI -164020 GOTO 40504030 REM PRINT NUMBER IN P6 IN HEX (0-65536)4040 R1=40964050 DE=""4060 P7 =P64070 R2=INT(P7/R I)40801F R2(0 THEN 41204090 IF R2<9 THEN 41204100 Dt=DC+CHR(R2+48)4110 GOTO 41804120 IF R2<10 THEN 41604130 IF R2>15 THEN 41604140 Di=DC+CHR(R2 r-55)4150 GOTO 41804160 DC="!!!!"4170 RETURN4180 IF RI = I THEN RETURN4190 P7 -INT(U(P7/111)-R2)*R I ) r 0 49999)4200 RI-RI/164210 GOTO 40705000 REM CONVERT HEX STRING IN HC TO DECIMAL

IN PI5010 P1=05020 FOR M9= I TO LEN (HL)5030 PI =PI*165040 P2=ASC(MID£(1-1£,M9, I))5050 IF P2<48 THEN 50905060 IF P2)57 THEN 50905070 PI =PI - (P2-48)5080 GOTO 51505090 IF P2<65 THEN 51305100 IF P2>70 THEN 51305110 PI =PI 4-(P2-55)5120 GOTO 51505130 PI =700005140 RETURN5150 NEXT M95160 RETURNREADY

Stock recordby bubblemethod

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A stock record in a stock control(continued on next page)

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application may comprise part number,description quantity in stock, unit priceand location in a warehouse. Such recordsnormally are stored in part numbersequence but if, for example, there isneed for the data to be printed in ware-house location number sequence, the datawill have to be sorted.

To perform a bubble sort the data hasto be in memory, and because each recordis made up of several items of data a two-dimensional array (table) is required tohold the records. Using the record sug-gested previously, the table may be shownpictorially.

(I)

(2)

(n)

Number

$(n,5)

Part Description QuantityIn Stock

UnitPrice

WarehouseLocation

There are five data items to a recordand the maximum number of records isdenoted by n.

The chosen data item which decides thesorted sequence is known as the key, whichin this example is warehouse location.

One way of performing the sort mightbe to compare keys and when two have tobe exchanged, swap over the other fourdata items in each record at the same time.This unfortunately, would result in moretime being spent moving data than isacceptable.

The solution I propose requires the keyto be put into another array with theposition of the record-row number inthe first array. The key is sorted and whenthe warehouse number is moved withinthe table, the row number is moved at thesame time.

These tables may be shown thus:

D$(n,4)

(I)

(2)

(n)

(I)

(2)

(n)

PartNumber Description

RowNo.

1(n,2)

WarehouseLocation

Quantity UnitIn Stock Price

Records are usually made up of a mixof alphabetic and numeric data whichcould necessitate the use of three arraysif numeric items are to be processed. Onearray would hold alphabetic data, thesecond would hold numeric data and thethird would hold the keys.

In my example, I wish to sort only thedata so that it can be printed in ware-house number sequence. After sorting,the array holding the keys is used as anindex to access the second array holdingmost of the data. The data to be used is:

Part No. Description Qty in Stock Unit Price Location1426 Product A 100 1.25 7168

1429 Product B 27 9.11 28721507 Product C 5106 0.60 1990

1861 Product D 28 2.18 48781943 Product E 87 5.00 9001

2086 Product F 72 0.28 20043166 Product G 13 28.47 1006

It can be seen from the listing that thesort routine needed only a few alterationsso that it handles tables instead of a list.

L1STNH10 REM BUBBLE SORT20 REM30 REM CONTROL40 DIM D$(7,4),1(7,2)50 GOSUB 100 !INPUT60 GOSUB 200 !SORT70 GOSUB 400 !PRINT80 GO TO 600100 REM INPUT ROUTINE110 FOR R-- I TO 7120 FC);1 C= I TO 4130 READ D$(R,C)140 NEXT C150 LET l(R,1)=R160 READ I(R,2)170 NEXT R180 RETURN200 REM SORT ROUTINE210 FOR PI -7 TO 2 STEP -1220 LET T2 -1(P1,2)230 LET F=0240 FOR P2=1 TO PI250 IF T2>I(P2,2) GO TO 300260 LET TI =1(P2,I)170 LET T2 -1(P2,2)280 LET T-P2290 LET F=1300 NEXT P2310 IF F=0 GO TO 370320 LET 1(T,2)=1(P1,2)330 LET l(P1,2)=T2340 LET 1(T,1)-1(PI, I)350 LET l(P1,1) =T1360 NEXT PI370 RETURN400 REM PRINT ROUTINE410 FOR RI -1 TO 7420 PRINT 05(I(RL1).! ).430 PRINT D$(I(RI,I),2),440 PRINT D$(I(R1,1),3),450 PRINT D$(I(RI,I),4),460 PRINT l(R1,2)470 NEXT RI480 RETURN500 REM DATA SECTION510 DATA 1426, PRODUCTA,100,1.25,7168520 DATA 1429 PRODUCTB,27,9.11,2872530 DATA 1507,PRODUCTC,5106,0.60,1990540 DATA 1861,PRODUCTD,28,2.18,4878550 DATA 1943,PRODUCTE,87,5.00,9001560 DATA 2086,PRODUCTF,72,0.28,2004570 DATA 3166,PRODUCTG,I3,28.47,1006580 RETURN600 END

READY

RUN NH3166150720861429186114261943READY

PRODUCTG 13 28.47 1006PRO DUCTC 5106 0.60 1490PRODUCTF 72 0.28 2004PRODUCTB 27 9.11 2872PRODUCTD 28 2.18 4878PRODUCTA 100 1.25 7168PRODUCTE 87 5.00 9001




This method of sorting records is notdifficult to program but is slow in opera-tion. The other problem in using thebubble sort is that, as all the data is heldin memory, the quantity of data whichcan be processed at any one time isdependent on the amount of free space.

This is possibly one argument forgetting as much memory as possible whenbuying a micro for business applications.It is possible to use the bubble sort with

C omput abit smmi

quantities of data larger than memoryfree space provided that some backingstore is available; unfortunately it in-volves a much greater processing time.

If backing store is available a differentsort technique can be implemented whichrequires only a small amount of memoryspace.

In the Kim project article in Issue 4, theword resistor appeared instead of registerin several instances.

Epic gamessome ideas

by Nick Hampshire

WHEREVER there is a computer you willfind at some time or another peopleplaying games on it. To many, this is awaste of computer time but there is nodoubt that playing games can be amentally stimulating and totally absorb-ing experience.

Computer games are of all kinds fromthe very simple to the highly complex.The simple games are mastered quicklyby the average person and, once mastered,lose most of their attraction. This accountsfor the fact that the classics amongcomputer games, like chess and Startrek,are long, complex and far from predict-able, and as such are never lacking infascination or challenge.

Real experienceA group of games which fall into this

category are the so-called epic games.The real classic of them, known only tothose with access to large machines, isAdventure, written by Will Crowther inFortran and occupying more than 120,000words (36 -bit) on a PDP-10.

I would suggest strongly that anyonewith the opportunity should play Adven-ture; it can be a real experience.

There is a common structure uponwhich all epic games are founded,drawing on the psyche and folk traditionof the player. The player is involvedactively and is identified as the centralfigure, a hero of national, international orgalactic importance.

Like a bookThe setting for the game is equal to the

importance of the hero and is oftendrawn from the world of fantasy.Equally, his opponents and allies are oftenendowed with supernatural powers andare drawn from the world of fictionalliterature.

The game usually involves our hero ina quest in which he must overcome greatdifficulties and perform great deeds to

achieve his goal. Thus Adventure involvesthe player in exploring a labyrinth ofcaves which may have between 25 and 100rooms. As you explore, you will encountertreasure, magical objects, and assorteddemons; you will find it advantageous totake some of the objects you find withyou as they will help you later in yourjourney.

Since the result of any action you takedepends on all your previous actions,this game is like a book with an infinitenumber of plots but the same basictheme.

The program for any epic game can bevery complex, both factors which tend torule out the possibility of writing such aprogram for a small machine like the Pet.This is not necessarily true, however, as ashortened version could be written forsuch machines by using techniques toreduce program space drastically.

NarrativeObviously, one can use all the tradi-

tional techniques like removing all REMstatements, deleting all spaces and re-using the same variable for severalpurposes. Those are all techniques whichwould horrify the orthodox programmerbut which result in the saving of a con-siderable amount of memory space.

By itself, however, this would not beenough to allow the running even of avery primitive epic program on an 8Kmachine, so we must look for othermethods.

One could write the whole program inmachine code but this is not to berecommended for any but the mostardent enthusiast, so a method is neededto reduce the size of the Basic program.

In an epic game we use a great deal ofdescriptive narrative, all of which iscontained in Data statements. Reductionof the number of words in each descrip-tion would result in a reduction of pro -


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Circle No. 176

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Circle No. 177

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11

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Circle No. 179

El One Day Courses on the Business riand Professional Use of Micro-computers

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Circle No. 181

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8K basic, 4K Static RAM 1K dedicatedvideo memory, 53 -key keyboard, upperand lower-case, graphics and gamingcharacters.for details: NIC Models, 27 SidneyRoad, London N22 4LP Tel. 01-889-9736

Circle No. 182


gram size. It would, however, reducegreatly the attraction of the program forany player. This method is not reallyfeasible;, if we look at the words used inPrint statements through such a programwe would find that about 70 percent ofthem are used more than once.

Since about 85 percent of the memoryspace used in an epic program is requiredfor Data statements, the observationthat so many words are used more thanonce provides us with a clue to a methodfor significant reduction in the size of ourprogram.

Each of the most common Englishwords could be assigned a one -characterabbreviation; this results in the com-pression of the description stored in eachData statement. A table of words andtheir abbreviations is then used by a sub-routine to expand and print the descrip-tion in plain English on the screen.

VocabularyThus, on the Pet, a vocabulary of up to

126 common words could be used withone alphanumeric or graphics characterfor each word. Some words, however,would occur only once and it would bedesirable to leave those words in theircorrect position in the Data statement.This could cause problems, since theprinting and expansion subroutine wouldnot recognise that word but only theindividual letters of the word, and insteadof printing that word would printa chain of words for which each individualletter was the abbreviation. To examinethis problem let us look at an example:The English sentence: "This is an example of a sentence

containing an unusual word"The vocabulary with associated abbreviations:This -A is -B an -Cexample -D of -E a -Fsentence -G containing -H word -1

A Data statement containing this con-densed sentence would then appear likethis:5630 DATA"ABCDEFGHC7UNUSUALI"and "This sentence is a new example"becomes 5640 DATA"AGBF3NEWD"

Whenever a word not in the vocabularyoccurs, it is preceded by a number indi-cating the number of letters in that word-thus "7UNUSUAL" and "3NEW". Theexpansion subroutine now can be con-structed easily to recognise words con-tained within a string of abbreviations.This method of text compression couldsave as much as 1,000 bytes on an 8Kprogram.

The use of a vocabulary opens anotherinteresting possibility in writing epic -typegames programs. This is to synthesise thetext output by the program and thus pro-duce an almost infinite variety ofsentences.

The trick is to arrange the vocabularyinto groups of words or phrases where thecontents of each group could all be usedin place of each other in a piece of text.Thus, instead of a piece of text we have a

series of pointers to groups of words orphrases; the broad meaning of thesentence can thus remain the same but thedetail and words differ every time it isused.

Which word or phrase is selected from agroup can be determined by a randomnumber generator or by a form ofweighted preference. The weighted pre-ference method would probably be bestsince, if properly designed, it wouldeliminate some of the grammaticalproblems which can occur during sentencesynthesis.

These ideas, I hope, will be of use toreaders who may be encouraged to try towrite an epic game, but I also hope that Ihave given some idea of the trend incomputer games, since I am sure that asthe price of memory and mass storagedevices like discs falls, it will not be longbefore we can all play Adventure on ahome computer.

Perhaps even more interesting is thepossibility of extending the principle ofthe epic game to produce the "electronicnovel"-the ultimate in escapism; nolonger does the reader identify himselfwith the hero-he or she is now the hero.

With an infinite amount of memory,high -resolution colour graphics and voiceinput and output, it is a very interestingconsumer market possibility within thenext 15 years, not to mention an equallyinteresting challenge for a new generationof authors.

Dams itemsfor PetDAMS of Liverpool not only stocks otherpeople's equipment but also produces itsown accessories for the Pet system. Theyinclude a joystick unit, page printer and625 external video adaptor.

The joystick with its machine code pro-gram gives full -control of screen printing,games and position -sensing. Averagingroutines in the software improve stabilityand accuracy and more than one unit canbe connected simultaneously.

The page printer unit allows a standardASCII printer running a 20mA loop inter-face to be driven by the Pet. A machine -code program causes the screen to becopied to the printer, though not thespecial Pet graphics.

The video adaptor allows the Pet screento be displayed on a standard UHF tele-vision set (tuned to channel 36), by con-nection to the aerial socket only. A 2Mco -ax lead and plug are supplied. Internaladjustments, factory pre-set to standardTV, allow connection to a wide variety ofmodels.

All three pieces of equipment have edgeconnectors and cables, cost £25 plus VAT,and have a delivery of 2-3 weeks.

Dams (Office Equipment) Ltd, 30/36Dale Street, Liverpool L2 5SF.


Computabits

PPX-Plus isuniversalin concept

[F the concept of a truly universal pro-grammer, using swappable personalitymodules to interface with differentmachines, makes you think of somedemon -coder with electrodes in his head,you're probably in the wrong business.

Either that, or of much too literal castof mind to cope with the Stag ElectronicDesign personification of its PPX-Plusfirmware programming system.

PPX-Plus can program any program-mable device, such as Proms, Fplas orsingle chip microprocessors, in any devicetechnology.

It consists of a mainframe containingpower supplies, drive circuits, interfaceelectronics, a VDU and keyboard, con-trolled by a microprocessor CPU.

The 'personality' module, whichmatches the programmer to the device tobe programmed, is inserted at the front ofthe machine, making it extremely easy toconvert from one device to another. Themodule contains specialised circuitry anddevice -specific information, such as volt-ages and timings.

Most of the electronics for doing theprogramming remains in the mainframeof the PPX-Plus. The software is dividedinto two operating systems, one control-ling the programming of Proms and Pals,and the other of Fplas, Fpgas, Fpls's andso on. The appropriate operating systemis automatically chosen by the software inthe 'personality' module.

The information to be programmedinto a device is stored in the RAM andmay be loaded via an 8 -bit parallel inter-face, a serial RC232C or 20mA currentloop interface, from a master deivce offrom the keyboard.

There is a number of input formats,


including those of the most commonmicrocomputer development systems andthey can be selected from the keyboard. Ifinterfaced to an MDS via its RS232Cinterface, the PPX can input directly fromthe MDS, avoiding the need for punchedtape.

Data in the RAM may be output via theparallel or serial interface to generatehard -copy printout or punched tape.

Editing of data in the RAM is achievedby changing it via the keyboard, or usinga re -locate mode to move around blocksof data.

Program patterns can be checkedeasily by using a list mode to display thecontents of master or slave VDUs, and theRAM.

Before programming a device, the PPXfirst will check it is unprogrammed. Itthen programs it to the manufacturer'srecommended specification. When pro-gramming is complete, the device is veri-fied against the RAM using the supplyvoltages and leads specified by the manu-facturer.

Normally all the locations of the deviceare programmed but should it be desiredto program only part of it, the address orP term range to be programmed can be setmanually. The programmer will then onlycheck, program and verify the locationswithin this range.

The PPX-plus can operate as a power-ful stand-alone system, or as a terminal toa microcomputer development system orminicomputer. It is able to support avariety of peripherals, such as tapereaders, punches, teletypes and printers.

Stag Electronic Designs is at Fellow-ship House, Tewin Road, Welwyn Gar-den City, Herts.

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Circle No. 183

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Circle No. 185

7!

The SORCERER

comes north for a demonstration of this flexible and reasonably -priced computer, contact (Basic Computing) Telephone Keighley 65094 (W. Yorks).

Our experience of Businessm applications, together with theml capabilities of the SORCERER, can give you a very effectivem small business system.m

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Circle No. 186

Mini ComputerCassettesat incrediblylow prices

Buy direct from themanufacturer and saveon top quality mini-computer cassettes.Thousands sold everymonth.Send for full details to:

PROFESSIONAL TAPES Ltd, Cassette House,329 Hunslet Road, Leeds, LSIO I NJ.

Telephone: Leeds (0532) 706066

Circle No. 187CHESS CHALLENGER '10'

PRICE £19995 for "THE WONDER" CHESS GAMEZ80A MICRO PROCESSORSOME OF ITS FEATURES INCLUDE:I. Ten levels of play including 'Mate in two'.2. Levels changeable during game.3. Random Computer Responses vary Every Game.4. Play from the bottom board or the top of the Board.

Choose either black or white.5. Does not permit illegal moves. Never makes an

illegal move according to all the rules of chess.6. Position verification by computer memory recall.7. Plays opening defences from chess books, i.e. Sicilian,

French, Ruy Lopez, Queen Gambit declined.8. Analyses as many as 3,024,000 board positions.9. Audio Feedback: Single tone each time you press a

key: Double tone when computer responds.TI Programmable L49'45 U.K. Microvision L99International Microvision L149'45Microprocessor Draughts and Backgammon also availablesae for details.CBM Pet 2001K, Texas TI59, 58 sae for details.KRAMER & CO, 9 October Place, Holders Hill RoadLondon NE4 IEJ Tel: 01-203 2473Mail order only, callers by appointment.

Circle No. 188

Dyna-Byte16K Dynamic RAM16K Static RAM16K Static RAM32K Static RAM32K Static RAM

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£198250ns £271450ns £266250ns £506450ns £470

80 x 24 video terminal, just add key-board and monitor £177.Cable set for video terminal E7.20

Post f ree. Add 8% VAT to all prices.

S.W.C. Electronic distributors, P.O.Box 30, London E.4.

Circle No. 189

Retinal displayis MagicWand for £5by NICK HAMPSHIRE

AN EXHIBIT mysteriously entitled theMagic Wand attracted a great deal ofattention at the West Coast Faire in LosAngeles (Practical Computing, January,1979). The reason for the interest lay inthe fact that the exhibit was for a veryingenious, low-cost alphanumeric com-puter display.

To look at, it was eight small lightemitting diodes on the end of a piece ofspring steel. Unless one knew, one couldwell be excused for thinking it a leg-pull inclaiming that it was a computer display-until the piece of spring steel was deflected,making it oscillate so that the LEDstraversed an arc a few inches long.

Then, instead of the LEDs appearing tobe on continuously, a line of text appearedin the area traversed by the diodes. Whatone was seeing was an example of what isknown as a retinal display.

Retinal display is a perfect example of anew technology being coupled with an oldprinciple to create a new field of applica-tions for that technology. The principle isthat on which the whole of the film indus-try relies-the fact that the eye retains animage for a short time after the image hasbeen removed.

Thus, if you move a light rapidly acrossyour field of vision, rather than seeing amoving point of light you will se a line oflight. The image at any one instant isretained long enough in the retina so thatit merges with all the other images whichfollow in the fraction of a second it takesto move the light.

False imageThe result is a false image. That effect is

produced with one LED and the piece ofoscillating spring steel. What is seen is anarc of red light apparently hanging in theair.

A LED has a great advantage over anincandescent lamp; it can be switched offand on very rapidly without having towarm up or cool. This fact makes itpossible to play some interesting gameswith LED and spring steel. If the LED isturned off and on rapidly, instead of anarc of light there is a series of dashes. Ifthe frequency is increased a chain of dotsof light is produced. Further increase infrequency returns us to what appears to

be an arc of light. It is this ability to pro-duce a chain of dots of light which is thefoundation of this display device.

Placing eight LEDs one above theother on the end of the piece of springsteel and turning them off and on syn-chronously at a certain frequency givesa display of eight parallel chains of dots oflight. This gives a matrix of dots and is thebasis on which an alphanumeric displaycould be constructed.

To do so, certain particular dots withinthe matrix would have to be turned off toproduce visible characters, and to do this acomputer is essential. Each column in thematrix is formed by the row of eightLEDs all on at the same instant. Not allthe LEDS, however, need be on duringthe on phase-that would produce an offdot in the matrix. Thus by turning on oroff the LEDs selectively in a precisely -timed manner, a display can be producedof, say, a line of text.

Simple displayA parallel eight -bit user port on the

computer can be connected via somedriver circuitry to the eight LEDs,allowing the timing and control to bedone entirely by software. One furtherpiece of circuitry is required to sense thereversal of direction of the piece of springsteel at the end of each sweep, this can bedone by an inertial switch connected to aninput line.

An inertial consists of a cantileveredpiece of wire of the correct mass andflexibility, which is forced to make aconnection at the end of each sweep by itsown inertia. That input triggers thecomputer after a suitable delay to displaythe line of text. For optimum viewing,this input should occur not less than 25times per second.

The software in its simplest form con-sists of outputting to the parallel port,byte by byte, the contents of a block ofmemory. If it is required to display a lineof 40 characters, with each characteroccupying an 8 x 8 matrix, it wouldrequire 320 bytes of memory. Charactergenerators could be built into the soft-ware but, of course, this kind of display isnot limited to alphanumeric characters;by increasing the number of I/O ports and




LEDs, a high -definition graphics displaycould be constructed.

One is not confined to placing theLEDs on the end of an oscillating strip ofspring steel. The display can be scannedby other mechanical means. Thus thediodes can be mounted on the edge of arotating drum, or a radar -type PPIdisplay can be constructed by placing a

Computabits

line of diodes along the radius of a rotat-ing disc.

Alternatively, this display also works ifthe viewer moves past the display, a factwhich opens -up some interesting advertis-ing applications.

Whatever technique is used it shouldprovide the computer enthusiast with anovel and unusual display for even thesimplest machine.

Essential itemsAN ESSENTIAL piece of equipment for anyserious hobbyist is an oscilloscope. TwoBritish -made instruments providing highquality at a price most people can affordare now available from Calscope.

The Super 10 dual -trace oscilloscopehas two vertical amplifiers with 10 mV/cmsensitivity and a band width of DC -10MHz (3 dB) and 10 MHz can be dis-played over the full screen area, a featurenot usually available with low-cost instru-ments.

ReliableComplementing the versatile amplifiers

is a fully -triggered timebase with sweepranges from 200 ns/cm to 100 nS/cm.Stabilised power supplies ensure reliableperformance and an unmatched accuracyof three percent for both voltage and timemeasurement.

The Super 6 single -trace has a verticalamplifier sensitivity of 10 My/cm to 50 V/cm

in 12 calibrated ranges; again, the band-width of 6 MHz can be displayed over thefull screen area. A versatile triggered time -base with 16 calibrated ranges of 1 µS to100 Ms/cm completes the equipment. TheSuper 10 costs £219 plus VAT, and theSuper 6, £162 plus VAT.

Both instruments are fully transistoris-ed, provide excellent performance para-meters and are always calibrated. Thefully -triggered timebase guarantees thatthe operator not only obtains 100 percentsteady reliable trigger from sine andsquare waves, but also from more com-plex wave forms such as pulse trains,while the instrument maintains its cali-bration.

Calscopes are available from MaplinElectronics Supplies, PO Box 3, Rayleigh,Essex; Audio Electronics, 301 EdgwareRoad, London W2; and Marshal'sElectronic Components, KingsgateHouse, Kingsgate Place, London NW6.

Advertisement IndexAbacus Computer Services 36 Keen Computers Ltd 30

Airamco Ltd 21

Al mare Data Systems 16 Limrose Electronics 57Lock Distribution 49

Beyts Logic Ltd 64 Lotus Sound 7

Byte Shop, The 4 LP Enterprises 8, 15, 63Lyme Peripherals 66

CCS Microhire 24Comart Ltd 5 Microd igital 34Commodore Systems Division 13, 48 Microsolve Computer Services 58Comp Computer Components 79 Millhouse Designs 66Compelec Electronics 50Computerbits Ltd 10 Nasco Sales Ltd 6, 8, 10, 12, 14

Compusettes 2 Newbear Computing Services 64

Computer Workshop 80Online Conferences Ltd 58

DAMS 36 Optronics 16

Data Efficiency Ltd 63

De Boer Elektronika 44 Padmede Ltd 20Pelco (Electronics) Ltd 66

Electronic Brokers Ltd 8 Personal Computers Ltd 63

Electrovalue Ltd 34 Petalect Ltd 10

Equinox 6, 20, 62 Petsoft 16

Euro-Cale 6 Rair Ltd 22Research Machines 17

Factor One 44Shelton Instruments 14

Games Workshop 34 Sintron Microshop Ltd II

Gate Microsystems 58 Sumlock Bondain 39

H.L. Audio Ltd 18 Tangerine Computer Systems 14

Technical Book Services 20

Infotech International 26Isher-woods 12 Video Software 64

Jade Computer Products 9 Xitan Systems 36


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Circle No. 190

Glossary

FailsoftFailsoft is essentially the same asgraceful degradation but providesless scope for double-entendres.Failsoft is a noun. As an adjective, asystem is failsoft if it switches it-self off in the event of breakdown,so that no important data is lost.Failsoft usually implies that thingscan be re -started from the pointat which the system broke down.Some machines fail softer thanothers.

FairchildThe Fairchild Instrument Co is oneof the big fish in the micro sea,though like many large corpora-tions it has not exactly seized theopportunities open to it, which iswhy Fairchild has a perfectlyrespectable line of microcom-puters (deriving from the F8)without setting the world on fire.

That might be about to change.Fairchild has suddenly becomevery active in this area, and is inthe process of litigation with DataGeneral, whose Nova instructionsets are used by Fairchild's latestI6 -bit micros.

Fairchild's other significance liesin its proximity to Silicon Valley.As a result, its alumni havespawned most if the top microand mini companies in the area,including Intel.

FaultYou will not believe this, but afault is what happens (or doesn'thappen) when something doesn'twork. In practice, the term usuallyrefers to a physical malfunction,which means a hardware defectlike a short-circuit, a duff piece ofsoldering or a broken wire. Bycontrast a bug (qv) is usually afault specifically in software.

FDXConventional abbreviation for fullduplex (qv).

FeedWhat happens to the sea -lions at1430 hrs. Or how cards and paperget into the computer. A card feedis the mechanical device which(wait for it) feeds cards into a cardreader. A paper feed is the mech-anism whereby paper is fed into aprinter. A front -feed is a particulardevice which allows you to stacka pile of single sheets on a printer,dropping a sheet at a time auto-matically into the printer.

FeedbackThe easiest way to get feedbackis to try giving an obstreperousinfant liver and spinach broth forits din -dins.

The word also has two lessfrivolous meanings. Feedback is

78

A PRACTICALGLOSSARY

Continuing the terminological gamut with F

what occurs when an output im-pulse is picked up and fed backinto the circuit as input. It happenswith any electrical transmissiondevice-frequently between elec-tric guitars and amplifiers. A bighand, please, for Jimi Hendrixand Pete Townsend who pion-eered its deliberate use in thatdepartment.

A second, more abstract, mean-ing of feedback is the getting ofinformation from one operationwhich can be used either to alterthat first operation or to initiateanother. This is why the letterspage of Practical Computing iscalled Feedback.

FerrantiHistorically significant in Britain.Ferranti's present interest is inmilitary and process controlsystems with its Argus minis andthe F100 micro, which was one ofthe earliest 16 -bit micros.

FFConventional abbreviation forform feed.

FieldA file consists of records, a recordconsists of fields. It is easy enoughto produce a logical definition ofa field-something like "an areawhere data of a given type will befound for processing or storage asa single entity". In practice, thedefinition is likely to be practicaland obvious. For instance, mem-bership records might comprisefields for name, address lines,membership number, and mem-bership fees paid. Or you mightset up the system at a greaterlevel of detail plus one field forsurname, two for first names, oneeach for house number, street,town, county, postcode, country... and so on.

FIFOI smell the blood of a jargon -monger. This whimsical termstands for "first in-first out"-a method of storing items of dataso that the first one entered is thefirst one retrieved. The averageuse of the term is for a FIFObuffer, which is typically a sequen-tial list of things queuing forprocessor's attention-instruc-tions to be executed, perhaps, orevents in the outside world.

FirmwareIs it a corset? No. Is it a toupeeadhesive? No. Is it a hardwiredprogram? Yes. Firmware is essen-tial software fixed in the computerin Read-only Memory (ROM). Forexample, the operating instruc-tions may be held on ROM-asthey are in the Pet; or a computer

which controls traffic lights mayhave its program permanentlyresident in the same way.

Because it is in ROM, firmwareexecutes very quickly-gettinginstructions from ROM is muchfaster than from ordinary read -unit memory. Since it is difficultor impossible to alter the con-tents of ROM, firmware has to beright before it is committed toROM.

FileAn attempt to organise relatedinformation; or a collection ofrecords. In practice, a file in com-puter terms is the essential inputfor a processing program. Somesystems require you to set upyour programs as individual files;you read the (program) file intomemory, and that file contains allthe instructions you need. Datafiles contain all the data a parti-cular program needs; a subscrip-tion program might use one fileof subscriber records. anotherwith subscription rates.

Filing systemAll but the smallest computershave system software which in-cludes at least some method oforganising files. The filing systemlays down the rules about how youstore and retrieve files. In parti-cular, it tells you how to relatethe organisation and structure ofa file to the patterns of access, butfor an exposition of this you'llhave to wait for indexed sequential(qv).

FillA field (qv) may be larger than theinformation you put into it. Anaddress field, for instance, may beset up to cater for large addresseswith up to seven lines of 35 charac-ters apiece; so a short addresswon't take up all the space avail-able. Some systems and someapplications require at least somedata in the unfilled area-so youhave to "fill" it, usually withmeaningless zeroes. This may alsobe called padding or packing.

Fixed discDescribed at length under dics(qv) ; a fixed disc is non -removable.A fixed disc is usually a fixed -headdisc, which means that each trackin the disc gets its own read/writehead. The alternative is movingheads, which move around thedisc surface to reach the data re-quired.

Obviously a fixed-head-or"head-per-track"-disc will pro-vide faster access to data; equallyobviously, they are considerablymore expensive than other discs.You can't afford one and probablydon't need one.

FlagFlag is what the editorial staff ofthis magazine do towards the endof the day. For a computer, a flagis a sequence of bits which signalthe beginning and the end of apiece of data, or indicate some-thing about it.

Typically, a flag is an indicatorattached to a data field; it is likelyto be a single hit position. Forexample, if you have a record tobe printed you might set a flag to"I". Your print program wouldthen hunt around the files lookingfor all records with the flag set.

Flip -FlopWoollies used to do good ones,and if you can afford them surfshops tend to have great flip-flops.The rest of us will have to make dowith something along the lines ofa bi-stable electrical component-which could be a toggle switch, orit could be a logic gate (qv). For-get it.

Floppy discFloppy discs are, as the nameimplies, a flexible storage medium,rather like the plastic 45 rpmrecords given away as promotions.Each disc lives in a protectivejacket; the read/write head passesthrough a slit in the cover. Wediscussed disc storage in depthunder our disc entry.

Floppies are in a range of sizesfrom 5i in. mini -floppies todouble -sided, double -density, full-size floppies. A normal mini-diskette holds about 71 KB; adouble -sided, double -densitymini holds four times that-280KB. Average 8 in. floppies gofrom a minimum of 250-315KB toa maximum of around 1.26 mega-bytes.

Access time for floppies isreasonably fast: they are not ex-pensive; they are easy to handleand to store. Rumour has it thatthe hole in the middle bends, too.

FlowchartA flowchart is a graphic represen-tation of a system or a program.As a concept it is brilliant. It isvery explicit an easily under-stood description of what ishappening-or what ought tohappen, since flowcharts areusually produced after you havedone some thinking but beforeyou write any code.

It is difficult to over -estimatethe importance of drawing a flow-chart. Everyone should learn flow-charting before they learn a pro-gramming language.

Flowcharts use a number of con-ventional symbols. The importantones are "process" boxes and"decision" lozenges.


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Circle No. 310

Documents

Cromemco Z -2D · 2019. 9. 27. · Microcomputermart Ltd., 29 Hanging Ditch, Manchester (061-832-2269) NewBear Computing Store, Bone Lane, Newbury, Berks (0635-49223) Xitan Systems