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ELECTRONIC DIGITAL COMPUTERA Tool for Research

D. V. I. FAIRWEATHERM.B. St. And., M.R.C.O.G.

SENIOR LECTURER

D. G. MILLARM.B. Durh., F.R.C.S.

FIRST ASSISTANT

DEPARTMENT OF OBSTETRICS AND GYNÆCOLOGY, KING’S COLLEGE,UNIVERSITY OF DURHAM, AND ROYAL VICTORIA INFIRMARY,

NEWCASTLE UPON TYNE

THE purpose of this communication is threefold:

firstly, to indicate the potentialities of the modernelectronic digital computer and to bring them to the noticeof workers in medical research; secondly, to dispel thewidely held illusion that these machines are beyond thecapabilities of people without special mathematical

training; and finally, to give a brief account of what isinvolved when a computer is employed.

THE AUTOMATIC ELECTRONIC DIGITAL COMPUTER

There are now many types of automatic electronic

digital computer situated mainly in university centres,government departments, and large industrial concernsthroughout the country. Our personal experience islimited to a Ferranti Pegasus computer which is the

property of the University of Durham. These machinesare expensive pieces of capital equipment, the modelmentioned currently costing about t80,000.A digital computer is so called because it handles

numbers in the form of a series of digits, in the same wayas a simple desk calculator. The precision of suchmachines can be increased indefinitely by allowing for alarger number of digits, and most digital computers willwork to an accuracy of at least 10 significant figures.Essentially, all computers comprise the following parts(fig. 1):

1. An input mechanism allowing data to be " read " by themachine.

2. A "store " or " memory " in which information (both

instructions and numbers) can be held in digital form. In

Pegasus this store is subdivided into 4000 individual units,each of which can accommodate a number containing 10

significant figures.3. An arithmetical unit in which prescribed calculations can

take place.4. A unit which controls the operation of the arithmetical

unit and the movement of numbers between the divisions of themachine.

5. An output device which allows the results of calculationsto be interpreted by the operator.The action of the computer is controlled by a " pro-

gramme " which is a series of instructions presented to

the machine in coded form. In Pegasus (and in many

Fig. 1-Diagram of the main parts of Pegasus

others) the orders are punched on five-hole teleprintertape which can be " read " into the computer by theinput mechanism. The orders are not obeyed at this stagebut are simply stored in the " memory ". When the timecomes, these orders are extracted and examined one byone by the control unit, which then causes the appro-priate arithmetical operation to be carried out. Theorders to be obeyed are normally extracted sequentiallyfrom the store. Certain " jump " orders break the regularsequence and cause the machine to take its next orderfrom some specified place in the store. This " jump " maysometimes be conditional upon the size or sign of aparticular number; for example, when a set of data hasbeen processed, an appropriate series of instructionsincluding a

"jump " orderwill cause the

programme to bere-entered at the

beginning to pro-cess a further set

of data.Some computer

installations pos-sess magnetic-tapeequipment whichpermits the stor-

age of intermedi-ate results or data.The values re-corded on the

magnetic tape canonly be inter-preted by the com-puter, but use ofthe tape permitsa great increase of

speed when deal-ing with a large amount of material. Magnetic tape can beread by the Pegasus computer at the rate of 10,000characters per second, whereas paper tape can be read atthe rate of only 200 characters per second.

PROGRAMMING

Digital computers can only handle problems whichhave been reduced to a number of elementary arithmeticalcalculations, and " the process of converting a problem tomathematical form properly belongs to that field of studywhich gave rise to the problem ". The first stage in

programming is, therefore, the reduction of the problemto a series of logical arithmetical operations; and thesecond stage is simply the writing down of the actualcoded instructions which the machine will have to obey.The process of programming can best be illustrated by avery simple example:

Suppose we wish to find the mean of a series of numberswhich have previously been punched on paper tape. We willassume that all these numbers are positive and that the end ofthe tape has been signalled by the punching of a negativenumber. The problem could be approached in the followingway. The computer would read the first number from thetape and examine its sign; if positive, it would then add thenumber into a " cell " of the store which had been set aside(sum cell). It would then add 1 unit into a second " cell",called the counter, jump back to the beginning of the pro-gramme, and read in the next number from tape. This process

Fig. 2-Flow diagram (see text)

1. The Ferranti Pegasus Computer: Programming Manual, 1955.

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would continue until, eventually, the computer encounteredthe negative number. It would then jump out of the previoussequence and divide the accumulated sum by the value in thecounter cell; finally, it would print the result of the last calcula-tion. This process can be illustrated by a flow diagram (fig. 2).

The final stage of programming must therefore consistin the translation of the flow diagram into actual codedorders which the machine can understand. Most peoplewill first learn to programme by using a form of

" auto-

code " which has the advantage of simplicity; in fact, theautocode can be mastered in two or three days. Mostautocode programmes on Pegasus, however, reduce thespeed of the machine to a twentieth or thirtieth of thatattained by a programme which uses the full order codeof the computer. This latter form of coding is somewhatmore complicated, and to learn to programme in thismanner requires two weeks’ full-time study.

INPUT AND OUTPUT OF DATA

Most data and programmes are presented to themachine in the form of punched paper tape which passesthrough an input mechanism (tape-reader); this consistsbasically of a series of photoelectric cells which canrecord the pattern of holes in the tape. The tape is pre-pared by a special perforator, the keyboard of whichresembles that of an ordinary typewriter. Some machines,however, can read direct from conventional punch-cards.Obviously any data other than purely numerical

measurements must be expressed in the form of a code,either literal or numerical. The accuracy of coding andpunching of data is all-important, as once a value hasreached the computer it will be regarded by the machine ascorrect. Although the computer can be programmed tocarry out certain broad consistency checks (which werefer to in more detail later), we feel strongly that datatapes should always be verified in some way-for example,by comparison of duplicates-to eliminate error. Mech-anical devices are available for making these comparisons.

Fig. 3-Example of printed results from maternity survey.

The Pegasus computer can be programmed to punchout the desired results on standard teleprinter tape. This

output may be fed directly into an "

interpreter " which

is connected to a page teleprinter. The layout of theprinted results is determined by the programme and canbe very various. The results can, for instance, be expressedin tabular or graphic form, with the appropriate titles.

PERSONAL EXPERIENCE OF A COMPUTER

Till now, we have mainly used the computer to analysedata collected in the course of a study of maternity in New-castle upon Tyne. This study, which extends over three years,will involve at least 15,000 cases and up to a hundred andtwenty items of information about each. The data consists ofnumerical statements such as height, birthweight, duration oflabour, &c., and coded information relating to occupationalstatus, housing, and various obstetric incidents during thepregnancy and labour. As a matter of detail, we punch thedates of birth, marriage, delivery, &c., as originally recorded,and use the machine to calculate the appropriate age, period ofgestation, interval between successive pregnancies, and so on.Once we had decided to use computer methods of analysis

and become reasonably proficient in programming, we re-examined our methods of recording data: we found that, bysome re-organisation, the data could be collected in a formwhich could be dealt with more economically by the computer.We next had to consider, in broad outline, the type of analysisrequired, and then develop suitable programmes. Our pre-liminary series of programmes has now been completed andtested. As programming had to be fitted in between ournormal clinical duties, this phase took more than six monthsto complete.We prepare our data along the lines indicated above, and

each case is recorded on about twenty inches of paper tape; wehave found that a reel of tape five inches in diameter containsthe data from 100 cases and can be conveniently handled. Thecases are read into the computer consecutively, and ages andvarious time intervals are calculated. The data is then com-

pressed and stored permanently on magnetic tape. A summaryis printed showing the survey reference number and certainselected obstetric abnormalities. The computer has been

programmed to examine most of the data and to reject caseswhich contain an improbable combination of facts. For

instance, if a patient is said to be unmarried and yet a date ofmarriage is recorded, the computer will come to a halt; thedata can then be corrected and " re-read ", or, if known to becorrect even though unusual, the computer can be made toaccept it. Altogether, there are about forty of these consistencychecks and we believe that they go a long way towards eliminat-ing error. While this is going on, the computer is accumulatingand storing thirty tables and frequency distributions, togetherwith certain values which will be necessary for statisticalcalculation. The time required for this sequence on one year’sdata (5000 cases) is about ten hours. Successive programmesusing this data from magnetic tape will occupy only one or twohours of computing time and will produce a further twentytables.

At the end of each run on the computer, the appropriatetables are punched out (for 30 tables this takes thirty minutes)and then printed, away from the machine. The time taken bythe printing depends entirely on the speed of the individualteleprinter.Our analysis results in the printing of tables, frequency

distributions, and correlation coefficients, &c. An example ofthe type of result is shown in fig. 3. This is an univariate

frequency-distribution of birthweight (in pounds) in all singlelive births. The summary in the first part of the table showsthe total number of cases, the lowest and highest weightsrecorded, together with the mean and standard deviation. Thenumber of cases in which the birthweight is not recorded isalso shown. In the lower part of the figure, the first columnrefers to the various groups of birthweight and shows the

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upper limit of each group; the second column shows thenumber of cases in each group; and the remainder is a histo-

gram of the distribution. In the latter part, each X represents1 % of the total cases, and the minus sign at the end of somerows indicate a 1/2% of cases.

DISCUSSION

The advantages and disadvantages of electronic digitalcomputers in processing data must be viewed in the lightof the other methods available. At present, the mainalternative is a card method, either manual or mechanical,such as Copeland-Chatterson or Hollerith cards. The

Cope.-Chat. card has the advantage of simplicity andallows the recording of additional information on the carditself. Sorting is manual-by

"

needling "-and thereforelimits the applicability of the method to small problemsdealing with limited numbers. The mechanical-card

methods, such as Hollerith, can deal with larger numbersand more complex problems but, as in the Cope.-Chat.system, a certain amount of predetermining of groups stillhas to be done if the number of cards used for each case isto be kept within reasonable proportions. For instance,age or duration-of-time groupings may have to bedecided and the group rather than the actual values thencoded. This may have the effect of obscuring differenceswhich are significant, or, alternatively, of suggestingdifferences which are, in fact, due only to the method ofgrouping. This objection can be ruled out by usingmultiple cards for each case; but this has obvious dis-advantages. Finally, when faced with such calculations asstandard errors, regressions, &c. on the Hollerith system,corrections and approximations have to be introducedsince quantitative data has been used in grouped form.This contrasts sharply with the computer which does thecalculations on the actual values recorded.

The computer has the further advantage that it cancalculate the values necessary for carrying out tests ofstatistical significance. The interpretation of these valuesand their actual significance is, of course, always a matterfor the operator. It can also be used to calculate intervals

-e.g., family spacing-automatically and rapidly. The

computer is particularly suited to repetitive types ofanalysis, and once a programme has been checked andshown to work satisfactorily, one can rest assured thatany further data processed will be dealt with in exactlythe same manner as before. This means that once an

appropriate library of programmes has been built up, allthat remains to be done is to select the appropriate pro-gramme and run it in with the new batch of data. Ifcertain easily altered figures (parameters) in the programmeare changed, the machine can be made to deal withvariations in size and complexity of tables.From what has been said, it will be evident that we have

found the computer method of analysis most satisfactory,and well suited to deal with the problems presented bythe type of study in which we are engaged.

CONCLUSIONS

Computer methods of analysis have many advantagesover other methods. The electronic digital computer canbe used by workers who have had no previous mathe-matical training. A repetitive type of analysis, or thesolution of complex mathematical problems, is relativelyeasy when tackled by computer methods.

Prospective users of the automatic digital computerare reminded that much time and thought must be

devoted to the given problem before beginning analysisof the data, or, indeed, before launching the study. Thisenforced discipline is no disadvantage and ought to

produce a higher standard of work.We are grateful to Prof. E. Grebenik, who first drew our attention

to the possibilities of computer methods; to Dr. E. S. Page and hisstaff for their valuable guidance and assistance at all times; to Prof.J. K. Russell under whom the present maternity survey is beingconducted; and to the Medical Research Council, the NewcastleRegional Hospital Board, and the Board of Governors of the UnitedNewcastle upon Tyne Hospitals who have given financial supportat various times. During one year of this study D. G. M. was inreceipt of a Junior Luccock Research Fellowship from the Universityof Durham.

GENERAL MEDICAL COUNCIL

At the opening of a meeting of the Council on Nov. 27,Lord CoHEN OF BIRKENHEAD, the president, said that theCouncil had recognised the degrees of M.B., CH.B.

granted by the University of Stellenbosch. Since May 31the registration of South African doctors had beeneffected in the foreign list of the Medical Register, in-stead of in the Commonwealth list as formerly.The President introduced the report of the Pharma-

copceia Committee, of which he is chairman. TheBritish Pharmacopceia, 1963, was now in proof and it washoped that it would be published during the summer ofnext year. It would be effective about six months later.

Weights and measures would be shown in the metricsystem only. Unfortunately the Bill to enable the conversionof Apothecaries’ into metric measure had lapsed in thelast session of Parliament. It had, therefore, had to bereintroduced. It included a clause enabling the Ministerof Health to make regulations which would govern thetables giving conversion figures.On publication of the Pharmacopceia in 1963, the Phar-

macopoeia Commission would dissolve itself. The rules

governing its appointment derived from a committeewhich was presided over in 1928 by a distinguished judge.The selection committee consisted of four personsnominated by the Council, three nominated jointly by thecouncils of the Pharmaceutical Society of Great Britain,the Pharmaceutical Society of Ireland, and the Pharma-ceutical Society of Northern Ireland, and two personsnominated by the Medical Research Council.The rest of the Council’s business was taken in camera.

Medical Disciplinary CommitteeThe Medical Disciplinary Committee met on Nov. 28-

30 under the chairmanship of the President.

APPLICATIONS FOR RESTORATION

The Registrar was directed to restore the names of JamesAlbert De Gregory and Alfred Fracon Williams. Applicationsfor restoration by Mrs. Grace Alison McCormack and WilliamRonald Pitt were rejected.

ERASURES

William Quirke, registered as of Mountjoy Lodge, Kildare,L.R.C.P.I. (1949), was not present to answer a charge of in-famous conduct in a professional respect. He had pleadedguilty at Stockton magistrates’ court on July 11, 1962, to

unlawfully obtaining by false pretences for the purpose ofself-administration certain drugs listed in the Fourth Scheduleof the Poisons Rules, 1960, a further similar offence being