Athira Sudarsan

7/28/2019 Athira Sudarsan

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Basic Terminology

Computer

A device that accepts input,

processes data, stores

data, and produces output,

all according to a series ofstored instructions.

Hardware

Includes the electronic and

mechanical devices that

process the data; refers to

the computer as well as

peripheral devices.

Software

A computer program that tellsthe computer how to performparticular tasks.

Network Two or more computers and

other devices that areconnected, for the purpose ofsharing data and programs.

Peripheral devices

Used to expand thecomputers input, output andstorage capabilities.


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Brief History

From ENIAC (Electronic Numerical Integrator andComputer) John Mauchly and John P Eckert,University of Pennsylvania (1943 - 1946)

For war purposes, ballistic trajectory

Weighted 30 tons, consumes 140 kwatts of electricpower, 15.000 square feet of space, only 5000addition per second

Not a digital computer, it was a decimal computer(analog)

John von Neuman proposed : EDVAC (ElectronicDiscrete Variable Computer) - first stored programcomputer -1945

1946 Von Neuman and his gang proposed IAS(Institute for Advanced Studies)


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ENIAC


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ENIAC


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IAS


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2.1. Evolution - History of Commercialcomputers

First Generation : 1950 Mauchly & Eckert developedUNIVAC I, used by Census Beureau

Then appeared UNIVAC II, and later grew to UNIVAC1100 series (1103, 1104,1105,1106,1108) - vacuumtubes and later transistor

Second Generation : Transistors, IBM 7094 (althoughthere are NCR, RCA and others tried to develop theirversions - commercially not successful)

Third Generation : Integrated Circuit (IC) - SSI. IBMS/360 was the successful example

Later generations (possibly fourth and fifth) : LSI andVLSI technology


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4th Generation Computers

1971-Present: Microprocessors

Miniaturization took over From SSI (10-100 components per chip) to

MSI (100-1000), LSI (1,000-10,000), VLSI(10,000+)

Thousands of ICs were built onto a single silicon

chip(VLSI), which allowed Intel, in 1971, to

create the worlds first microprocessor, the 4004,which was a fully functional, 4-bit system that ran at

108KHz.


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2.1. Evolution - history of commercial computers

Table 2.1

Approx Speed

Generation Time Technology opr/sec)

--------------------------------------------------------------------------1. 1946-57 Vacuum tube 40,000

2. 1958-64 Transistor 200,000

3. 1965-71 SSI & MSI 1,000,000

4. 1972-77 LSI 10,000,0005. 1978- VLSI 100,000,000

--------------------------------------------------------------------------


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Functional Units

Figure. Basic functional units of a computer.

Processor

ANDARITHMETIC

LOGIC

CONTROL

OUTPUT

MEMORY

INPUT


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INPUT UNIT:

Converts the external world data to a binary format, which

can be understood by CPU

Eg: Keyboard, Mouse, Joystick etc

OUTPUT UNIT:

Converts the binary format data to a format that a commonman can understand

Eg: Monitor, Printer, LCD, LED etc


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Memory Unit Store programs and data

Two classes of storage

Primary storage (RAM, SRAM and DRAM) Fast

Programs must be stored in memory while they are beingexecuted

Temporary memory-data lost when power gone

Higher cost

Secondary storage larger and cheaper(storehouse)

Stores bulk of programs and databases.

Floppy disk, hard disk and Magnetic tape,CD,etc


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Central Processing Unit (CPU)

Control unit+ ALU

Brain of computer

Perform all calculations

Takes all decisions

Control all units

Eg:-Intel Pentium


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Arithmetic and Logic Unit (ALU)

Most computer operations are executed in

ALU of the processor.

Load the operands into memory bring

them to the processor perform operation

in ALU store the result back to memory

or retain in the processor.

Registers

Fast control of ALU


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Control Unit

All computer operations are controlled by thecontrol unit.

The timing signals that govern the I/O transfersare also generated by the control unit.

Control unit is usually distributed throughout themachine instead of standing alone.

Operations of a computer: Accept information in the form of programs and data through

an input unit and store it in the memory Fetch the information stored in the memory, under program

control, into an ALU, where the information is processed

Output the processed information through an output unit

Control all activities inside the machine through a control unit


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Framework


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Get

instructio

n from

memory

Framework


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Read

from

register

file

Get

instructio

n from

memory

Framework


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Read

from

register

file

Use ALUGet

instructio

n from

memory

Framework


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Read

from

register

file

Use ALUGet

instructio

n from

memory

Access

memory

Framework


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Read

from

register

file

Use ALUGet

instructio

n from

memory

Access

memory

Framework

Write register file


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What *exactly* is memory?

Interface:

reads: input

output writes:

input

output

Variation Multi-ported

May read or write multiple items at the same time

Must add inputs / outputs

Address

Data contained in address

Address & Data to place in address

None


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ALU DATAPATH and CONTROL Processors Datapath

Control unit

Datapath-collection of units-memory, programcounter, registers, Arithmetic logic unit, and

control unit. Control unit-how data flows through datapath.

Memory unit: holds data and instructions

Various locations-specific address

Store and give data to datalines in response to address givenby address lines and control signals.

Read and write signals


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ALU DATAPATH and CONTROL

Data saved

Address LocationsAddress

0006

0005

0004

0003

0002

0001

Address lines

MEMORY UNIT

Read signal

Write signal

Data lines


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Registers Temporary high speed memory.

Store instructions, data, results.

General purpose Registers(GPRs)-data/address Instruction register

Program counter (PC) instruction pointer

Holds address of current or next instruction

Incremented after each fetching


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Control unit Flow of information

Generates control signals

ALU control, memory write, memory read,input read, output write, etc.

ALU Arithmetic and logical operation

Integer arithmetic add, subtract etc.)

Bitwise logic operations (AND,OR, NOT, XOR)

Bit shifting operations

Operands

Code from control unit

(Control signals)

Output


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Working of ALU based on Datapath

and control

Register(2)

Register(1)

Register(0)

A B

R

Write(2)

Write(1)

Write(0)Read(2)

Read(2)

Read(2)

F D

M hi h


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Memory hierarchy


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Memory Hierarchy

Memory Hierarchy- comparing cost and

performance

Response time, cost and size

4 major storage levels Internal-processor registers, cache

Main- RAM

Secondary storage-online

Tertiary offline storage

M Hi h


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Memory Hierarchy Top level-CPUs General purpose registers

Fast access

Small size Expensive

Level one cache size small, but greater than CPU reg.

Level two and level three caches

Main memory Low cost, general purpose (RAM)

Secondary Solid state memory Cheaper, large in size

Virtual memory Work like main memory, hard disk, slower, low cost


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Cache memory

Cache very high speed memory used by CPU

to reduce the average time to access memory

smaller, faster memory which stores copies of the

data

Read or write from cache if copy present-faster


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If requested data in cache- cache hit -faster

Otherwise- cache miss -access from originalmemory-slower


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Cache memory

Cache- small Based on the principle locality of reference

Same value or place where it is stored is accessed

often Temporal locality-at one point of time a particular

memory accessed- likely that same location

referenced again in near future

Spatial locality -if one memory accessed at a time,likely that nearby memory loc. referenced in near

future.

so store a copy of data in nearby loc. to cache


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Cache memory- Bookshelf analogy

College libraryhard disk

Your book shelf- main memory Your study table- cache memory

Easiness of access

Book shelf (main) easier than college shelf (harddisk)

Study table (cache) easier than book shelf

Temporal locality- one book in bookshelf usedagain and again in nearby time, so keep on

study table Spatial locality- more books in book shelf may b

used, better to keep on study table


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Main memory

Working memory of CPU

RandomAccess Memory

Read Only Memory RAM-main memory

Constructed from ICs

Need electrical power to maintain data Volatile memory

Access time nanoseconds.

RAM divided into two-SRAM,DRAM


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SRAM Flipflops-storage

Data unchanged unless new data entered DRAM

Capacitors-storage

Data changes due to charge leakage

Refresh storage elements periodically

ROM Permanent storage

Non-volatile-data retains even after power down(off)

Quick and accurate

Data cant be altered

PROM


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PROM Already programmed or blanked state

Program entered externally

Never be altered

Unique purpose programming

Mistakes cannot be corrected

EPROM Purchased blank or programmed one

Can be erased if needed

Data/ programs retrieved several times

Reprogram- erase data by a UV light burst

Erased and mistakes corrected

Can add improvements in program

EEPROM-electrically erasable PROM Erased and programmed by electric current

No need to remove from computer for programming


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Secondary memory

No direct access by CPU

Computer uses I/O channels to access

Non-volatile Hard disk drives

Time taken to access data-few

milliseconds Optical storage-CD,DVD drives, USB,

floppydisks, magnetic tapes etc.


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Virtual memory Operating system uses hard disk space acting like main

memory-Creates the illusion that more memory existsthan is available in system

Main memory as a cache for secondary storage

To extend the size of physical memory

If a program is large, divide into segments

Active segments in main memory Inactive segments in secondary memory

If not in main memory, copied from secondary storage

New segment replaces non using segment in main

memory OS swaps segments btw main and secondary memory

Called virtual memory


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Virtual memory Memory Management Unit (MMU) controls

virtual memory Managed both in hardware (MMU) and thesoftware (The operating systems)

CPU generates the logical address

Two types of addresses in virtual memorysystems

Virtual addresses Referenced by processes

Physical addresses Describes locations in main memory (real) Memory management unit (MMU)

Translates virtual addresses to physical address


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Advantages of Virtual Memory

Simplified addressing scheme: theprogrammer does not need to bother about the

exact locations of variables/instructions in the

physical memory.

It is taken care of by the operating system.

For a programmer, a large virtual memory will

be available, even for a limited physical memory.

Simplified access control


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Operating system Program acts as interface btw user and

hardware Collection of programs coordinates h/w and s/w,

regulates the way user communicates

Microsoft windows, Mac OS X, Linux, Android

Important part of OS- kernel

Controls low level process

How memory read/written

Order of execution How info received and sent by

i/p o/p devices

O ti t


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Operating system User interface- allow user to control and use

programs

Graphical (icons) or text based(command line) Windows and MS-DOS

Application programming interface- set ofservices and programs, let apps interact

OS takes control of system-direct to h/w Stays in background

Provides channels of communications to applicationprograms

Classificationof OS

Based on user interface- GUI,TUI Based on number of users the computer can support-

time sharing OS

OS divides the working time of CPU for the users


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Operating system

Multiprocessing OS is similar to a time sharing

OS except more than one CPU available

Time sharing OS- allows resources (CPU,

applications etc.)to be shared among severaljobs(Supercomputer)

Batch processing OS-jobs by sequence of

control statements in machine readable form Industries

Real-time OS-respond quickly to external world

signals -Aeroplane


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Operating systems

MS-DOS-16 bit, command line interface

WINDOWS- 32 BIT-GUI

OS/2-32 bit

UNIX-multiuser, multitasking OS Scientific research, engineering etc.

LINUX- stable OS

Hierarchical relation btw


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Hierarchical relation btw

H/W,S/W and User

User

Applicationprograms

Utilityprograms

OS

ComputerHardware


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Functions of OS

Starting the computer: bootprogram Diagnostic programs-for primary memory

Attached system devices

Prepare computer to normal working mode

Running application programs: Steps1. OS accepts user command

2. reads from secondary memory to RAM

3. OS give control to application to execute

4. Control restored to OS when program ends


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Running utility programs: Give user control over various features of

computer

Resident utility pgms- in RAM (INPUT MONITORINGPROGRAMS)

Transient pgm- read into RAM upon request (FILECOPYING PROGRAM)

Managing files:

information organized into files

Need to organize these


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Programming concepts

Computer programming

Skill of writing useful, maintainable, extensible

instructions by computing system to perform a

meaningful task High level or low level (machine)languages

Written in programming language

Computer understand Machine codeprogram-set of binary

But difficult for human

Di d f hi l


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Disadv of machine language Difficult ot understand or debug

Entry slow

Difficult to remember codes

Long programs

Errorprone

Preferred for less computations only Assembly language

Use meaningful words-mnemonics (ADD,SUB etc)

Unique program for each processor

Advantages

Faster execution

Easy to understand and debug


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Disadv of ALP Skilled programmer required

Not portable program Lengthier

Preferred for medium computations only

High level languages- similar to

grammatical languages-English

BASIC, FORTRAN, COBOL, PASCAL,C,

etc.

Operation oriented rather than computeroriented- user friendly

Portable- no need for knowledge of CPU

f


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Advantages of HLP:

Instructions very clear

Easier, faster- to write Portable

Not CPU oriented

Universal language- easier to document Preferred for large computations

Limitations

Thorough idea about rules of language Lower execution speed

More h/w, s/w support

Costlier as features increases


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MICROPROCESSOR

All functions of CXPU in an IC

Intel 4004-4 bit IC- first mp

ROM,DRAM, I/O devices, 4 bit CPU

Intel 8008-8 bit mp

Intel 8085- popular mp


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8085 Microprocessor

Features of 8085

No: of data lines - 8

Word length - 8 bit

No: of address lines - 16

Operating frequency - 3.125MHz

Supply voltage - 5V

Technology - NMOS

No: of pins - 40


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Organization of 8085

Register section- temperory storage

ALU- h/w for computations

Interface section-communicates to outside

Timing and control section- coordinating

and controlling various activities

Architecture of 8085


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Architecture of 8085


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Description of Architecture of 8085

Registers 6 GPRs - 8 bit-B,C,D,E,H and L

16 bit- Reg pairs- BC,DE, HL

one accumulator, one flag reg. 2 16-bit reg- Stack pointer and program counter

Accumulator-A 8-bit, part of ALU

Store data to perform operations

Store result of operation


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Program counter(PC) 16-bit -instruction sequencing

Memory pointer-16 bit address Sequence execution

Points to memory address from which nextinstruction to be fetched

One byte fetched, PC incremented by one to pointto next

Stack pointer (SP)

16-bit- memory pointer

Points location in main memory-stack Stack to store current status of

microprocessor


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Instruction register/Decoder Temporarily stores current instruction of program

Decoder interprets instruction- converts to machinecode

Timing and control unit

Provide clock signals-maintain timing inside

mp

Control unit generate signals to carryout

instruction

Connection btw blocks open /closed


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Arithmetic logic unit

Takes data from memory/GPRs and accumulator

1.Arithmetic: Addition, subtraction, increment,decrement, compare

2. Logical : AND,OR,EXOR,NOT,SHIFT/ROTATE,

CLEAR

Flag register 5 flip flops- set or reset after an operation

Zero(Z), Carry(CY), Sign(S), Parity (P), Auxiliary

Carry (AC) flags

Accumulator+ Flag register Program Status Word(PSW)

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Athira Sudarsan