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 COMPUTERS, COMPUTING AND CAREERS 
 
 by 
 H. C. Br ear ley- 
 
 March 10, 1965 
 Revised March 23, 1965 
 
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 OF ILLINOIS • URBANA, ILLINOIS 
 
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r JMe^ REPORT NO. 171 
 
 COMPUTERS, COMPUTING AND CAREERS 
 
 by 
 H. C. Brearley 
 
 March 10, 1965 
 Revised March 23, 1965 
 
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 TABLE OF CONTENTS 
 
 Computer Mechanisms 1 
 
 People Who Build Computers 4 
 
 Uses of Computers 5 
 
 Computer Programs 7 
 
 People Who Write Computer Programs 10 
 
 Other Computer People 12 
 
 Women in Computing 13 
 
 Education for a Career in Computing 13 
 
 Suggestions for Further Reading 15 
 
FOREWORD 
 
 The Department of Computer Science receives numerous inquiries 
 about computers from high school and college students. These questions 
 cover the history and physical form of computers , the uses of computers 
 and career opportunities for computer people. This paper attempts to 
 answer these questions, at least in part and to indicate other sources 
 of information. 
 
Computer Mechanisms 
 
 Men have been attempting to reduce the labor of arithmetic calculations 
 for centuries. Some early efforts were directed toward paper-and-pencil techniques 
 such as the development of logarithms in 1614 by James Napier. Other efforts were 
 directed toward simple mechanical devices such as the ancient abacus and the 
 slide rule. Simple adding machines using gears were invented by Blaise Pascal 
 in 1642 and by Gottfried Wilhelm Leibnitz between 1671 and 1694. 
 
 Among the first attempts at large-scale mechanized computation were 
 the "difference engine" and the "analytical engine" conceived by the Englishman 
 Charles Babbage (1792-1871). In 1822 Babbage made a small five-digit difference 
 engine which could generate a table of values of any function whose second 
 difference* was a constant, without human intervention except at the start of 
 the problem. He worked, with the support of the British government, on a larger 
 version capable of calculating to 20 places any function whose sixth difference 
 was a constant, but it was never completed. One difficulty was that it required 
 a large number of small precision mechanical parts similar to the gears, ratchets 
 and levers in present-day desk calculators. Before the project was abandoned, 
 much time and money were spent developing the necessary precision machining 
 techniques which were otherwise not available at that time. One author estimates 
 that if made according to plans, the difference engine would have weighed two tons. 
 
 *A function whose second difference is a constant is one whose second derivative 
 is a constant, namely a second-degree polynomial. Many tables can be approx- 
 imated quite accurately over a limited range by a second degree polynomial, and 
 over longer ranges by higher degree polynominals. 
 
 -1- 
 
In 1834 Babbage conceived the idea of an "analytical engine" which was 
 a mechanical computer capable of performing an indefinitely long sequence of 
 additions , subtractions , multiplications and divisions in any order under the control 
 of sequences of punched paper cards. Babbage estimated that its speed would be 
 one addition per second and one multiplication per minute. Many detailed drawings 
 were made, but the analytical engine was never built. 
 
 Another pioneer was the American Herman Hollerith (1860-1929). He 
 refined the principle of storage and transmission of information by means of punched 
 cards which had been used earlier in Babbage' s engines and before that in the loom 
 developed by Jacquard for weaving complicated patterns into decorative fabrics. 
 Hollerith developed card-reading, counting and sorting equipment which was used 
 in the United States census of 1890. His name is preserved in the ubiquitous 
 "Hollerith" punched cards, more often referred to as "IBM"cards . 
 
 Babbage's efforts in the 1830's were unsuccessful in part because he 
 attempted to extend mechanical techniques such as those used in the now-familiar 
 mechanical desk calculator to much larger and more complex machines. More 
 successful results were obtained during World War II when electrical techniques 
 were used. The first electrical computers used electrical relays to perform the 
 calculations. They also used punched paper tape and electrically operated type- 
 writers , innovations which had been perfected earlier in connection with the 
 printing telegraph network. A number of relay computers were built at Harvard 
 University and Bell Telephone Laboratories. The Harvard Mark I relay computer, 
 which was built in 1939-1944, was 51 feet long, 8 feet high and could add in . 3 
 seconds. It was used largely to compute tables. 
 
 -2- 
 
The relay computers were followed by vacuum tube computers . The 
 first was ENLAC (for Electronic Numerical Integrator and Calculator) built at the 
 University of Pennsylvania at the end of World War II. A tremendous improvement 
 in speed was obtained because a vacuum tube can switch a current on or off in 
 microseconds (millionths of a second) while a relay requires milliseconds 
 (thousandths of a second) . A vacuum tube computer called ILLIAC (I) was built 
 at the University of Illinois in 1949-1952. It contained about 2,700 tubes and 
 could perform 1,400 multiplications or 11,000 additions per second. The first 
 mass-produced computers were built in the early 1950's, and they were vacuum 
 tube computers. These included the well-known UNIVAC and IBM 650 computers. 
 
 Computers built since the late 1950's use transistors instead of vacuum 
 tubes to achieve increased reliability and speed. One of the larger and faster of 
 the new computers is ILLIAC II, built at the University of Illinois between 1957 
 and 1963. It can perform 160,000 multiplications per second or 330,000 additions 
 per second. It contains about 50,000 transistors, 125,000 diodes and numerous 
 other parts, and cost about $4,000,000. Transistor computers are also commer- 
 cially produced in a variety of sizes. Costs vary from the low ten thousands of 
 dollars for a desk-size computer to millions of dollars for a room-sized computer. 
 
 The next generation of computers will continue to use transistors, but 
 may also use integrated circuits (composed of transistors, diodes, resistors and 
 their connections manufactured all at once) , super-conducting materials operating 
 at temperatures near absolute zero, and optical techniques. 
 
 -3- 
 
People Who Build Computers 
 
 People who build computers usually work for a computer manufacturer, 
 although a number of one-of-a-kind computers have been built at various 
 university and research laboratories . There are a dozen or so computer manu- 
 facturers in the United States, and many more in Europe, Japan and elsewhere. 
 
 One important group of people associated with the construction of a 
 computer are the men who determine the organization of the computer, that is, 
 the functions of the various parts and how they are connected to each other. 
 Such people usually have bachelor's, master's or doctor's degrees in mathematics 
 or electrical engineering. 
 
 Another very important group designs the electronic circuits of the 
 computer. Most computers are composed of a few simple circuits (one to a 
 dozen transistors each) which are repeated hundreds or thousands of times and 
 connected in many different ways. The circuit designers decide how many basic 
 kinds of circuits are needed. Then they design them, build samples and test 
 them in the dozens of arrangements in which they will be connected in the 
 finished computer. The circuit designers are typically electrical engineers, 
 assisted by technicians. However, a circuit design group working with newer 
 devices such as thin film, superconducting or optical devices may include 
 physicists, metallurgists and others. All except the technicians are usually 
 college graduates , often with advanced degrees . 
 
 After the detailed organization of the computer has been determined, 
 and its circuits have been designed, drawings or tables are made showing the 
 
 -4- 
 
connections of every transistor and every wire. This takes many months and 
 many people. Then one or more prototype computers is constructed from these 
 drawings, which also takes months. At each of these stages difficulties usually 
 arise, which must be corrected. Eventually the design is considered satisfactory 
 and factory production begins . 
 
 Uses of Computers 
 
 For many years it has been popular to divide computer calculations 
 into two broad classes—scientific and data processing. The scientific class 
 includes such things as calculating the movements of the planets, ballistics 
 of shells, rockets, and satellites, solution of differential equations representing 
 heat or current flow in nonuniform media, calculations in nuclear physics, etc. 
 The data processing class includes sorting and counting as in the census of 
 1890, payroll calculations, updating inventories, searching lists for pertinent 
 entries, etc. 
 
 Some of the computers of the vacuum tube generation were designed 
 specifically for one class or the other. The "scientific" computers emphasized 
 high-speed arithmetic. The "data processing" computers emphasized high-speed 
 input and output. Today this distinction has become less important. Even a 
 "scientific" computer has to read in its data and instructions and print its 
 output, and both may be voluminous. And "data processing" computers have 
 been called upon to perform more operations which require considerable logical 
 (or computing) capability. 
 
 -5- 
 
A third, more recent class of computer applications is in so-called 
 "real-time" problems. A "real-time" application is one in which the computer 
 is connected directly to some process, receives its input data from the process, 
 and produces output data to control what the process does next. The delay 
 between computer input and computer output is usually fractions of a second. 
 One such process is the control of an oil refinery. The computer may divide its 
 attention among a number of jobs. It may control the raw material and fuel flow 
 so that a cracking tower operates correctly, a fairly simple job. As a more 
 complicated job, it might also decide each week, on the basis of market prices, 
 costs and other data, how much of each grade of gasoline, kerosene and other 
 products to make to maximize profits . 
 
 The distinction between the three classes is more academic than real. 
 For example, airlines' reservations computers keep lists of seats sold and 
 unsold, and keep passenger lists for each flight for some months in the future. 
 They also respond via special leased telephone lines to requests for information 
 from keyboards in ticket offices all over the country, and to requests to sell 
 a seat. A response to an inquiry usually takes only a fraction of a minute. 
 Hence, this example embodies both "data processing" and "real-time" aspects. 
 
 The extremely wide range of problems which computers have been used 
 to solve might lead one to expect that there are a large variety of computers 
 manufactured. There are a large number of models of computers available from 
 different manufacturers, but the small ones are all more or less alike and the 
 big ones are all more or less alike. Sometimes special features are needed for 
 
 -6- 
 
special jobs; for example, the airline reservations computer has to have 
 equipment to enable it to communicate over telephone lines to keyboards at the 
 various ticket offices, and it needs an unusually large memory to store all the 
 reservation lists . 
 
 But the big differences in the behavior of computers are determined 
 not so much by the physical equipment as by the instructions fed to them . A 
 sequence of these instructions is called a computer program. These instructions 
 are usually punched into cards or paper tape and then fed into the computer. 
 The computer then runs and produces answers in seconds, minutes or hours 
 depending on the length of the program. By feeding programs to a computer one 
 after the other one may make the computer perform first one job, then another . 
 This steady flow of different jobs may continue 24 hours a day in a large 
 installation, interrupted occasionally to test the computer to make sure it is 
 working correctly or to fix a malfunction. 
 
 Computer Programs 
 
 A human being tells a computer what to do by writing a program . He 
 does this by writing for the computer a sequence of detailed instructions. The 
 instructions have to be detailed, complete and unambiguous. Such phrases as 
 "do it like I told you on Monday," and "you know what I mean," are generally 
 useless . 
 
 A computer program is written in a "language." There are several 
 types of computer languages. The most laborious to write is the language the 
 machine itself understands , called machine language. The instructions in 
 
 -7- 
 
machine language are very elementary. The following examples show some common 
 machine language instructions and one way they might be abbreviated for punching 
 onto cards to feed into the computer. 
 
 Add the number in location X in the memory to the number in the 
 accumulator* and leave the result in the accumulator. (ADD X) 
 
 Store the contents of the accumulator in location X in the memory. 
 (STO X) 
 
 Fetch the number from location X in the memory and put it in the 
 accumulator. (CLA X) 
 
 Using these three instruction types , one may write a program to form the sum 
 
 S-A+B+C+D 
 
 and store the result in location S in the memory thus:** 
 
 CLA A 
 
 ADD B 
 
 ADD C 
 
 ADD D 
 
 STO S 
 
 Computers usually have several dozen types of instructions , and some of them are 
 
 considerably more complicated than this simple example indicates. 
 
 Machine language is laborious to write because it reguires that the 
 
 calculation be broken down into such minute steps. Other computer languages 
 
 have been developed which are easier for humans to use. One of the more popular 
 
 *The accumulator is the main register of the computer, the place where the number 
 being worked on is stored. It corresponds to the main dial of a desk calculator. 
 
 **The instructions shown here are actually written in "assembly language" which 
 is a variation of machine language. 
 
is FORTRAN, which stands for formula trans lator. For example, instead of writing 
 the sequence of five machine language instructions in the example above, one can 
 write in FORTRAN 
 
 S=A+B+C+D 
 
 which is both easier to write and easier to read. The hitch is that the computer 
 does not understand FORTRAN, so a FORTRAN program must be translated into 
 machine language before it can be executed. The computer itself performs this 
 translation under the supervision of a translation program. The translation program 
 must be written in machine language, but this has to be done only once. Other 
 computer languages have been developed which are particularly convenient for 
 arithmetic (ALGOL) , for manipulation of strings of letters and numbers (LISP) , for 
 guidance of computer-controlled tools (APT), and so on. 
 
 Most computers can execute about 10,000 to 1,000,000 instructions per 
 second. A human programmer can write and correct about 100 instructions a day. 
 The ratio of speeds is about 30,000,000 to 1. However, it does not require 
 30,000,000 programmers working full time to keep one computer busy. One 
 reason is that the computer programs contain loops. A loop is a part of a program 
 which is executed over and over again. For example, a program which processes 
 registration data for 20,000 students at a university who take an average of five 
 courses each will contain at least two loops. One loop will be repeated once 
 per student, or 20,000 times. The other loop will be repeated once per course 
 or 100,000 times. 
 
 -9- 
 
Another reason it does not take 30,000,000 programmers to keep one 
 computer busy is that whole programs are used over and over. The university 
 registration program would be used at the beginning of every semester. A 
 program which processes incoming checks in a bank would be used for several 
 hours each banking day. Also the translation programs are used often, as are 
 many others . 
 
 People Who Write Computer Programs 
 
 One of the most geographically dispersed occupations associated with 
 computers is computer programming. Programmers work for computer manufacturers 
 and for organizations that rent or buy computers. There is probably at least one 
 computer and one computer programmer in most towns in the United States over 
 50,000 people. 
 
 Activities of programmers vary over a wide range. At one end of the 
 scale is the programmer associated with a small machine at a small factory or 
 bank. He would write most of his programs in one or two languages developed 
 for that machine and that kind of business. The necessary language translation 
 programs will have been supplied by others, frequently by the computer manu- 
 facturer. At the other end of the scale the programmer associated with a large 
 installation or a computer manufacturer will write in more languages for more 
 elaborate computers , and he may develop new computer languages and translators 
 for them . 
 
 The programmer has the task of translating vague and sometimes 
 contradictory directions from human beings into precise computer instructions 
 
 -10- 
 
that will lead to the desired result. This is not always easy. It may require 
 great perseverance and tact to get a complete and unambiguous description of 
 the problem from the humans. It also requires diligent attention to detail to 
 write an error- free computer program. 
 
 Training in computer programming is available in a variety of forms. 
 Computer manufacturers offer programming courses for their computers , partic- 
 ularly to personnel of organizations that lease or buy them. In some cities 
 "commerical schools" teach programming as they teach desk calculator 
 operation, typing and shorthand. Programming training is available at most 
 colleges and universities, where it varies from four or six-week noncredit 
 "short courses" to one-year credit courses meeting three or four hours a week. 
 Some universities also offer courses in theory of languages, writing translator 
 programs, etc. A few universities offer degree programs in computer science. 
 
 A college degree is very desirable for a programmer, but it need not 
 necessarily be in mathematics or computer science. A degree in the field of 
 the prospective employer's business may be just as good. For example , an 
 electrical manufacturing company would probably hire engineers, business 
 administrators and mathematicians as programmers , and an accounting firm 
 would hire accountants and mathematicians. Of course, people who are trained 
 in both computing and in the area of the prospective employer's business are in 
 great demand. 
 
 -11- 
 
Other Computer People 
 
 There are a number of other occupations associated with computers. 
 One of them is servicing computers . Although the individual elements which 
 make up a computer (transistors, resistors, wire, etc.) are very reliable, 
 there are many thousands of them , and every so often one of them fails . Most 
 medium- and large-scale computer installations have their own repairmen or 
 they have a service contract with the manufacturer which assures them of the 
 services of a "field engineer" or "customer engineer" on a few hours notice. 
 The same serviceman often comes once a day or once a week to run programs 
 to check the operation of the computer and to do preventive maintenance. 
 Computer servicemen are usually trained as electronics technicians in trade 
 schools, the armed services, colleges or training courses run by their employer 
 They live all over the country to be near the computers they service — there is 
 probably at least one living in every city over 100,000. 
 
 Computer operators are another occupation. These people load 
 programs into the machine, start it, remove printed output, and sometimes 
 do minor repairs. This is a less skilled job than the computer programmer or 
 serviceman. For the smaller computers , an operator may learn his job from 
 another operator, but for the larger computers, an operator usually attends a 
 manufacturer's training course. Some computer operators work at night, since 
 most large computers are kept running 16 or 24 hours a day. 
 
 -12- 
 
Women in Computing 
 
 Many women are employed in the computer business . Almost every 
 occupation related to computers requires a lot of thinking and very little muscle, 
 so women are in as much demand as men. A large fraction of computer programmers 
 are women. Women mathematicians engage in computer design and hold many other 
 jobs. Women are less numerous in computer engineering and servicing. 
 
 Education for a Career in Computing 
 
 The educational requirements of various computer occupations have 
 been mentioned in earlier sections. Most of them require a college degree. 
 
 A high school student who is headed for a career in computing should 
 take the courses needed for admission to the college and curriculum of his choice. 
 He should study these admission requirements early in his high school career to 
 make sure that he will satisfy them. If after fulfilling these requirements he 
 still has time for more courses , we suggest that he take more college preparatory 
 mathematics courses, and in the case of prospective engineers, more physics and 
 chemistry. 
 
 Some college students who are interested in computers enroll in a 
 curriculum in computer science and follow that curriculum. Others enroll in 
 other curricula and take computer-related electives . Those students concerned 
 with computer programming and programming languages should select such 
 electives as programming (frequently offered at two or more levels), theory of 
 compilers, Boolean algebra , set theory, logic, calculus, differential equations , 
 
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numerical methods , probability and statistics, linguistics, information storage 
 and retrieval, pattern recognition, etc. Those concerned with computer organi- 
 zation and engineering should select from the courses listed above plus such 
 courses as methods of computer arithmetic, theory of digital machines, automata 
 theory, pulse and logical circuits, solid-state electronics, etc. 
 
 At the University of Illinois , computer-related courses are offered by 
 the Department of Computer Science. Administratively this department is a part 
 of the Graduate College, but the contacts with the College of Engineering are 
 very close. For example, essentially all engineering undergraduates take a three- 
 hour course in computers and programming called Introduction to Automatic Digital 
 Computing. The department offers many other courses in computing: 
 
 Introduction to Theory of Digital Machines 
 
 Digital Computer Methods for Data Processing 
 
 Introduction to Numerical Analysis 
 
 Boolean Algebras With Application to Computer Circuits I 
 
 Boolean Algebras With Application to Computer Circuits II 
 
 Intermediate Programming 
 
 Digital Computer Electronics 
 
 Theory of Computer Design and Circuits: Logic 
 
 Theory of Computer Design and Circuits: Memory 
 
 Logical Design and Automatic Digital Computer Circuits 
 
 Advanced Programming 
 
 Mathematical Theory of Data Processing 
 
 Analytical Problems in Numerical Analysis 
 
 Seminar in Automata Theory 
 
 Threshold Logic 
 
 Seminar in Applied Mathematics 
 
 Students in the Engineering College can add a strong computational flavor to their 
 
 curricula by using some of these courses as technical electives. It is also possible 
 
 -14- 
 
to obtain a bachelor's degree in Mathematics and Computer Science in the College 
 of Liberal Arts and Sciences. This curriculum has a strong mathematical core plus 
 a substantial number of courses drawn from the above list. 
 
 Graduate study in computer science is available at a few universities, 
 including the University of Illinois. The work generally consists of two parts. One 
 part is taking advanced courses in subjects such as those mentioned above; the 
 other part is doing individual research on some particular aspect of one of these 
 subjects, and writing up the findings as a thesis. 
 
 Suggestions for Further Reading 
 
 Encyclopaedia Britannica . See articles on Babbage, binary numbers, computing 
 machines, logarithms, slide rule, tabulating machines . 
 
 Benrey, Ronald. Understanding Digital Computers . JohnF. Rider Publisher , 
 New York , 1964, 166 pp. $5.45. An introduction to digital computer construc- 
 tion. Many details such as full adders, half adders, instruction decoders 
 described clearly at an elementary level with diagrams and equations. 
 Bibliography. Recommended. 
 
 Bernstein, Jeremy. "Profiles - The Analytical Engine, The New Yorker , 
 Oct. 19, 1963, pp. 58-96; Oct. 26, 1963, pp. 54-108. An excellent 
 layman's introduction to the whole computer field. Includes some simple 
 Fortran programs, and considerable history of computer development. 
 
 Bowden, B. V. Faster than Thought . Sir Isaac Pitman and Sons, London, 1953, 
 414 pp. Written by Bowden and a large number of contributors. An extensive 
 survey of British computer technology from the beginning through 1952. A 
 67-page appendix contains a description of Babbage's analytical engine 
 written in 1842 . 
 
 Burck, Gilbert. "The Boundless Age of the Computer, " Fortune , March 1964, 
 p. 101; April 1964, p. 140; May 1964, p. 153; June 1964, p. 112; Aug. 1964, 
 p. 125; Oct. 1964, p. 120. A series of articles on the economic effects of 
 computers . 
 
 -15- 
 
Desmonde, William H. Computers and Their Uses . Prentice-Hall, Englewood 
 Cliffs, N J., 1964, 296 pp. $10. A survey of the whole field of computing 
 on a fairly elementary level. Over half the book is devoted to verbal descrip- 
 tions of computer applications. The remainder covers history, machine 
 construction, logic, etc. Unfortunately there is no bibliography. 
 
 Eckert, W. J., and Rebecca Jones . Faster, Faster . McGraw-Hill, NewYork, 
 1955, 160 pp. A fairly nontechnical description of the IBM Naval Ordnance 
 Research Calculator (NORC) . 
 
 Jacker, Corinne. Man, Memory and Machines . Macmillan, NewYork, 1964, 
 126 pp. $3.95. " 
 
 McCracken, D. D A Guide to Fortran Programming . John Wiley, NewYork, 
 1961, 88 pp. $2.75. A very lucid text on the widely used computer 
 programming language named FORTRAN. 
 
 Morrison, Phillip, and Emily Morrison. Charles Babbage and His Calculating 
 Engines, Selected Writings by Charles Babbage and Others . Dover, NewYork, 
 1961, 400 pp. $2. 
 
 Richards, R. K. Arithmetic Operations in Digital Computers . D. VanNostrand, 
 New York, 1955. A thorough treatment of computer arithmetic. 
 
 Stibitz , George R. , and Jules A. Larrivee. Mathematics and Computers. 
 McGraw-Hill, NewYork, 1957, 228 pp. $5. A good, serious introduction 
 to computers, particularly for a reader with some mathematical background. 
 Contains a general bibliography plus a long bibliography on computer 
 applications . 
 
 -16- 
 
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