Father Of The Computer Age
Howard H. Aiken’s Mark I announced to the world the power of the computer
HOWARD H. AIKEN HOLDS AN AMBIGUOUS POSI tion in the history of the computer. Although a number of historians have declared that his first machine—the IBM ASCC (Automatic Sequence Controlled Calculator), known today mainly by the simpler name Mark I—inaugurated the computer age, many accounts of the birth of the computer either ignore his role altogether or consider him to have belonged to a pre-computer age.
Aiken was a giant of a man: in his physical stature, his force of will, his originality of mind, and his achievement. Standing erect at six feet and some inches tall, he towered over most of his students and colleagues. Graced by nature with a huge dome of a head, he had piercing eyes, crowned with huge beetling and somewhat satanic eyebrows. When he spoke to you in repose, he wore old-fashioned tortoise-rimmed pince-nez eyeglasses, attached to a black tape that went around his neck. In the course of conversation he would emphasize a point he was making by staring at you for a moment in silence; then, blinking his eyes and giving his nose a slight twitch, he would cause the glasses to fall, revealing his full face. You then knew that you had his undivided attention.
Aiken was the type of person who related to people by extremes. When he met you, almost from the very start you were placed at either the top of his scale or the bottom; there was never a middle ground. On a scale from 1 to 10, Aiken would almost at once rate you as a 0 or an 11. People reacted to him in the same way and on the same scale. His students and associates either admired him and established friendly relationships or found him “impossible.” Friends and colleagues and former students on the “plus” side remained loyal and devoted for the rest of their lives, and Aiken himself cherished longterm relations. Those on the “minus” side tend to remember just those occasions when he was intransigent and difficult.
Only a person endowed with strong internal force could have survived the rigors of Aiken’s adolescence and early adulthood. His life permitted no middle ground, and he judged others by his own demanding standards, inviting an equal sort of judgment from them. Only someone with a strong personality and a tough-minded aggressiveness could have forced a reluctant Harvard to become a computer center. Only a person such as Aiken could have been a trumpeter announcing the dawn of the computer age.
Was Aiken the “inventor” of the “computer,” or even the “first inventor” among others? Those questions are extremely complex and raise important problems of exactly what is meant by “inventor,” “computer,” and “first” inventor. Partisans of various early machines are currently arguing—somewhat fruitlessly, it must be confessed—over which machine was the first computer. Among the claimants are the Atanasoff-Berry ABC, the Colossus machines developed in England for code breaking during World War II, Konrad Zuse’s Z3 in Germany, and the Eckert-Mauchly ENIAC. At the very least Aiken was certainly an inventor of one of the early machines from which the modern computer has developed. What is more significant in the annals of history, in the view of many of the people involved, and of historians and later computer scientists as well, is that Howard Aiken and his machine ushered in the computer age in which we live.
Standard works on computer history contain statements such as “the digital computer age began when the Automatic Sequence Controlled Calculator (Harvard Mark I) started working in 1944,” and “the Harvard Mark I … marked the beginning of the era of the modern computer” and “the real dawn of the computer age.” In 1980, in one of the first major scholarly studies on the origin of the digital computer, the historian Paul Ceruzzi concluded that “if one were to look for a date from which to mark the dawn of the computer age,” one might well choose “August 7, 1944, when the existence of such machines was first made known to the world”—that is, the day the Mark I was publicly announced.
Like many pioneers, Aiken had a multifaceted career that influenced a number of different aspects of his new field. Collectively these broader innovations were so important that they actually outweigh in significance the features of any of the machines with which he was associated. The portrait of such an innovative and influential scientist is thus of double interest: as the presentation of the life and character of an extraordinary individual and as the record of an important phase in the birth of the time in which we live.
Howard Hathaway Aiken was born in Hoboken, New Jersey, on March 8, 1900, an only child. When he was just entering his teens, his family—consisting of him, his parents, and his maternal grandparents—moved to Indianapolis. Soon after, his father left home and was never seen by his family again. Young Aiken was just ready to start high school when it became his responsibility to support his mother and grandparents. This meant quitting school to go to work. He got a job installing telephones and continued his education by means of correspondence-school courses. Later in life he enjoyed telling how as an adolescent boy he had installed all the phones in the red-light district of Indianapolis.
Someone in the school system recognized Aiken’s intellectual brilliance, especially in mathematics, and helped him obtain a night job with the Indianapolis Light and Heat Company, permitting him to go back to school. Thereafter, during high school, he worked a 12-hour night shift and attended school during the day. He not only had time to do his homework but whiled away hours by learning to knit and knitting his own socks.
When Aiken graduated from high school, in 1919, the school officials once again became active in his behalf. The superintendent of public instruction wrote a letter about him to every Midwestern public utility located in a university town. As a result Aiken was offered a job with a utility company in Madison, Wisconsin, and that, he said, was why he went to the University of Wisconsin. The family moved to Madison, where he supported himself and them working as a watch engineer on the night shift of the Madison Gas and Electric Company while attending college during the day. In 1973, shortly before Aiken’s death, Henry Tropp (a math professor at Humboldt University) and I conducted a three-day interview with him in which he told us of his joy in discovering that Wisconsin had adopted an 8-hour day that was “much easier” than the 12-hour shift in Indianapolis.
After his graduation in 1923 Aiken became the company’s chief engineer. As he put it, “I was promoted from switchboard operator to chief engineer overnight.” During the next 10 years he held a succession of better and better positions in different companies in the electric-power industry, rising in his profession. Nevertheless, despite his success, he found the managerial side of engineering unsatisfying and decided to go back to school. He spent a year in the physics department at the University of Chicago but found it a disappointing experience. In 1933—at the age of 33 and much older and more experienced than most graduate students—he enrolled in the Ph.D. program in physics at Harvard.
At Harvard he became part of a group interested in such matters as the thermionic emission of electrons, the physics of antennas, reflections from the upper atmosphere, and the like. His thesis topic was a study of the conductivity of vacuum tubes, specifically the theory of space-charge conduction. He began teaching while still a graduate student, and on receiving his Ph.D., in 1939, he was appointed faculty instructor, Harvard’s equivalent of assistant professor. He rose steadily to full professor. By the time he received his Ph.D., however, his focus of interest had already shifted from electron physics to the design and use of computers.
The shift, Aiken said, came about while he was doing research for his thesis. The subject of the thesis, he explained, was space charge, “a field where one runs into [partial] differential equations in cylindrical co-ordinates … in nonlinear terms, of course.” Before long his thesis research came to consist primarily of “solving nonlinear [differential] equations.” The only methods then available for numerical solutions of problems like his made use of electromagnetic desk calculators about the size of today’s cash registers, and calculations like those he needed were “extremely time-consuming.” It became apparent—”at once,” he said—that the labor of calculating “could be mechanized and programmed and that an individual didn’t have to do this.” He also realized that a computing machine would be of great use in solving pressing problems in many scientific fields, in engineering, and even in the social sciences.
By April 1937 Aiken had progressed far enough in his general thinking and design to seek support from industry in producing such a machine. In preparation he drew up a proposal stating the need for it, the principal features of its mode of operation, and its general method of solving problems. His philosophy was later expressed in an assignment he drew up for one of his Harvard classes in computer science. “The ‘design'” of a “computing machine,” the students were informed, “is understood to consist in the outlining of its general specifications and the carrying through of a rational determination of its functions, but does not include the actual engineering design of component units.”
In this clear statement the primary concerns were the logic of the machine, its mathematical operations, and its general architecture; its actual technological specifications were secondary. To judge from all the information available, Aiken’s design would not have specified what particular components or even what types of components—mechanical, electromechanical, or electronic—were to be used or how the various components would be linked. He essentially would have specified the need to perform certain types of mathematical operations and to have a means of programming them so they could be performed in a certain predetermined sequence, and he would have indicated the need for storing certain tables of numerical data. The design could apply equally well to a machine constructed of mechanical, electromechanical, or electronic components or any combination of them.
As is generally well known, Aiken’s eventual machine was built by IBM and was based on electromagnetic relays rather than vacuum tubes. It may seem odd that a graduate student in the physics of vacuum tubes should have had his machine operate with relays rather than tubes. The reason was, as he explained it to us, that if the Monroe Calculating Machine Company had undertaken to build his machine, it would have been largely mechanical; if RCA had done it, it would have been electronic; but since IBM turned out to be willing, the functioning elements were electromagnetic, of the type IBM used in its business machines.
As Aiken drew up his proposal for a new sort ot caku lating machine, he had to be sure that the physics department would find a place for it. The department was not at first very enthusiastic; the department chairman reported to Aiken that one of the laboratory technicians, Carmello Lanza, had asked why on earth Aiken wanted to build such a machine when there was already one in the Physics Research Laboratory and nobody had ever used it.
Aiken at once sought out Lanza, who took him into “the attic” and showed him a set of calculating wheels. These, it turned out, had been built a century earlier by Charles Babbage for use in his Difference Engine, a machine that had been designed to embody many of the features of today’ computers. The set of wheels had been presented to Harvard by Babbage’s son in 1886, on the 250th anniversary of Harvard’s founding. Aiken went at once to Widener Library and, for the first time, came to learn of Babbage’s ideas.
On April 22, 1937, Aiken made contact with his first choice for a prospective builder of his machine, the Monroe Calculating Machine Company, America’s foremost manufacturer of calculating machines. Although the chief engineer was enthusiastic, his management was not interested. Aiken’s next try was IBM. There his first contact was with James Wares Bryce, known affectionately within the company as “the father engineer.” Bryce had been granted more than 400 patents, an average of about one per month since beginning his career in 1900. In 1936, on the centenary of the U.S. Patent Office, he was honored as one of the country’s 10 greatest living inventors. Aiken’s meetings with him were the first steps toward the construction of the Automatic Sequence Controlled Calculator.
As all histories of IBM make clear, no important decision was ever made at IBM without the explicit approval of its president, Thomas J. Watson, Sr. Watson was a powerful figure, a titan in his sphere, endowed with just as forceful a personality as Howard Aiken. Anyone who has read anything at all about these two men will know that there had to be an eventual collision course and a terrible clash. It would happen after IBM built Aiken’s dream machine.
In November 1937, encouraged by Bryce, Aiken submitted a formal proposal to IBM. In it he set forth the need for such a supercalculator and the kinds of problems it would solve. He then explained the mathematical functions or series of steps that the machine would have to perform and the types of mathematical operations it would be called on to execute. He stressed the need to make it able to perform its work in a series of predetermined automatic sequences, controlled by a set of specific instructions. In today’s language, we would say that the machine was to be programmed. This quality was eventually embodied in its formal name, Automatic Sequence Controlled Calculator.
In those days the word computer meant a human being, usually a female, armed with a desk calculator and a book of tables, not a machine. Which is why most of the computer engineers, designers, and programmers in the 1940s referred to the new types of computing devices as “calculating machines.”
When IBM first agreed to build Aiken’s machine, it was envisaged that the company would supply the parts but much of the assembling would be done in the Harvard machine shops. This soon proved impractical, and construction was done at IBM’s plant in Endicott, New York. A senior engineer, Clair D. Lake, was assigned to oversee the project. Francis E. (Frank) Hamilton was responsible for most of the practical decisions, and Benjamin M. Durfee did most of the actual wiring and assembly of the components. Beginning in 1938, Aiken spent long weekends and two whole summers in Endicott, explaining the operations the machine would have to perform and helping design the circuits that would let it execute the commands.
Over the next years he also spent many days in Endicott helping translate his requirements into machine componentry. It was soon apparent that although the IBM engineers who were assigned to the task of translating Aiken’s theoretical specifications into practical machine reality were extremely gifted men, skilled in circuits and componentry, they knew very little mathematics. They could not really understand the kinds of problems the new machine was being designed to solve.
In April 1941 Aiken, an officer in the U.S. Naval Reserve, was called to active duty, so he could no longer pay regular visits to Endicott. He was assigned to the Naval School of Mine Warfare, in Yorktown, Virginia, and he designated Robert V. D. Campbell, a graduate student in physics at Harvard, to serve as his deputy during the final stages of construction. He was extremely fortunate in getting Campbell. Campbell had a solid background in physics and was adept at applied mathematics, and he made a number of creative decisions on his own. His already important role became even greater in February 1944, when the giant machine was disassembled and shipped from Endicott to Harvard, where it was installed in a large room in the basement of the Physics Research Laboratory. Campbell was now in full charge of the machine until Aiken was assigned to Harvard by the Navy in the spring of 1944, and he programmed and ran the first problems. He also took responsibility for working out all the initial problems of error and unreliability. His share in the final testing and operation of the ASCC/Mark I was much larger than is apparent in most histories of the computer.
The first two problems set for the new machine came from Ronald King, a physicist specializing in electromagnetic theory and the physics of radio transmission, and James D. Baker, an astronomer whose specialty was telescope and lens design. King recalls that the problem he sent Campbell was to “work out some integrals.” By the time the machine computed those results, however, it had been turned over to the Navy, and its programs and outputs had at once become “classified.” As a result, King, who had no Navy clearance, could not gain access to the work the computer had done for him. He got, he told me, “a couple of pages of tables with numbers on them, and that was all.” Still, they were “very useful.” Baker’s problem was the design for the Army Air Forces of a high-power telephoto lens in which corrections and adjustments would be made for effects such as changes in atmospheric pressure with altitude.
In April 1944 Aiken was transferred from Yorktown to Cambridge, where his new assignment was to take charge of the computer operation; in May the machine was turned over to the Navy for the duration of the war and became an official unit of the Bureau of Ships under Aiken’s command. By August the Mark I was in full operation with a large staff of Navy personnel, including a number of officers, among them Grace Hopper (see “Amazing Grace,” by J. M. Fenster, Fall 1998 issue), and Richard M. Bloch, who became the chief programmer.
To celebrate the completion of the machine and its successful installation at Harvard, a ceremony of dedication was planned, with many admirals, government officials, Harvard faculty, and others present, a formal luncheon, and speeches by President J. B. Conant of Harvard, Aiken, and Thomas J. Watson. When Watson arrived in Boston the day before the ceremony, he found that Harvard had issued a news release identifying Aiken as the primary inventor of the new machine and downplaying IBM’s contribution. It made him so angry that he threatened to boycott the event altogether, and Conant, Aiken, and other Harvard scientists had to rush in to calm him. In the end Harvard issued a revised news release acknowledging the importance of the IBM inventors, and IBM published a booklet about the machine stressing the company’s contribution. At the ceremony Watson stole the limelight by making a gift to Harvard of $100,000 to defray the future costs of operating and maintaining the computer. At the time, a Harvard professor earned approximately $10,000 a year, so this was the equivalent of 10 professors’ salaries—or about $1,000,000 in today’s currency. The total cost of the machine to IBM is usually reckoned to be around $200,000 in 1930s dollars.
This was a very large sum of money. In retrospect it is astonishing that IBM would have invested so much in a proposal by a young Harvard instructor just finishing his graduate work, especially when the engineers who were actually building the machine considered it “screwball.” Who could be sure it would actually function as Aiken predicted? Furthermore, it was understood from the start that this project would not lead to a new product line at IBM; it was going to be a contribution to science and engineering and in no way a source of potential profit.
One reason IBM had embarked on such a costly adventure with no guarantee of success was that Bryce was a true believer in Aiken’s proposal. He had no doubt that Aiken’s dream would be made a practical reality. And Watson relied heavily on Bryce’s judgment.
In 1944 and 1945 Mark I ran almost continuously, 24 hours a day and seven days a week. The wartime problems the machine was asked to solve included studies of magnetic fields associated with the protection of ships from magnetic mines and mathematical aspects of the design and use of radar. No doubt the most important wartime problem was a set of calculations for implosions brought from Los Alamos by John Von Neumann. Only a year or more later did the staff learn that these calculations had been made in connection with the design of the atomic bomb. Mark Fs outstanding success and backlog of jobs led the Navy to ask Aiken in early 1945 to design and construct a second such machine. Aiken did so. It became known as Mark II.
Mark I was gigantic, an imposing sight, 8 feet high, 51 feet long, and almost 3 feet deep. A portion of it is on permanent exhibit in the main lobby of the Science Center at Harvard University; this gives only a partial notion of its original grandeur. It weighed five tons, used 530 miles of wire, and contained 760,000 parts. Relying on technology developed by IBM for statistical and accounting business machines, it used traditional IBM parts such as electromagnetic relays, counters, cam contacts, card punches, and electric typewriters but also incorporated elements of a new design, including relays and counters never before used in an IBM machine. These were smaller and faster than those in use. The input consisted of a punched tape, and the output was a series of punched cards or a printout from a standard IBM electric typewriter. The computer had 2,200 counter wheels and 3,300 relay components.
Its operation was powered by a long, horizontal, continuously rotating shaft that made a hum that has been described as being like that of a gigantic sewing machine. In later language, Mark I would be described as a parallel synchronous calculator. It had a word length of 23 decimal digits, with a twenty-fourth place reserved for an algebraic sign. Calculations were done in decimal numbers with a fixed decimal point. Its 60 registers for the input of numerical data (the constants that appear in any algebraic or differential equation) each contained 24 dial switches corresponding to 24 digits. For any problem these had to be set by hand.
The location of each of these 60 registers was assigned a number, so that the instructions could use the location to identify a number being called up in the course of a calculation. The operative portion of the machine consisted of 72 additional registers, or “accumulators.” Each register was made up of 24 electromagnetic counter wheels, again providing the capacity for 23-digit numbers, with one place reserved for a sign. This second set of panels comprised both the store or storage and the processing unit.
A typical line of coding in the program would instruct the machine to take the number in a given input register (either a constant or a number in the store) and enter it in some designated register in the store. If there already was a number in that register, the new number would be added to it. The programmer had a code book, stating the designation of each location and each operation.
There were separate devices for multiplication and division and four tape readers. One was used to feed the instructions into the machine, and the other three held tables of functions and could supply values as needed. There was also provision for the interpolation of values given on the tapes. Thus there were built-in “subroutines” (as Aiken called them) providing for a number to be converted by some built-in function (such as a sine, an exponential, a logarithm, or raising to some power) before being entered into the store.
Programs were fed into the machine by punched tape. The programmer first reduced the problem to a sequence of mathematical steps and then used the “code book” to translate each step into the necessary coding or instructions. Mark Fs instructions were essentially single-address instructions. Those who wrote programs for Mark I later recalled that the process was very much like programming later computers in machine language.
Although similar in many ways to later machines, Mark I incorporated one feature that today’s sequenced program computers do not have: If you did not explicitly tell Mark I to go ahead and execute the next instruction, it stopped. Programmers had to enter a seven after each command to instruct the computer to proceed. If the machine didn’t get that signal or some other automatic signal, it just stopped dead and waited for directions. From some points of view this was a tremendous advantage; for example, it was wonderful for debugging step by step. Mark I was the only sequenced program computer to include this feature.
The chief programmer, Dick Bloch, kept a notebook in which he wrote out pieces of code that had been checked out and were known to be correct. One of his routines computed sines for positive angles less than π/4 to 10 digits. Rather than use the slow sine unit built into the machine, Grace Hopper simply copied Bloch’s routine into her own program whenever she knew it would suit her requirements. This practice ultimately allowed the programmers to dispense with the sine, logarithm, and exponential units altogether. Both Bloch and Bob Campbell had notebooks full of such pieces of code. Years later the programmers realized that they were pioneering the art of subroutines and actually developing the possibility of building compilers.
Mark I continued to function at Harvard for 14 years after the war, producing useful work until it was finally retired in 1959. During that time, it also served generations of students at Harvard, where Aiken had established a pioneering program in what was later to be called computer science—with courses for undergraduates and graduate students leading to a master’s degree or a Ph.D. Many important figures in the computer world were introduced to the subject on the Harvard Mark I.
In retrospect, Mark I’s greatest significance may have lain in its dramatic public demonstration that a large-scale machine could actually perform an automatic sequence of calculations according to a program, and do so without error. Mark I did not, however, influence later computer technology as a machine since its computing elements were made of electromagnetic relays rather than of vacuum tubes, such as were used in ENIAC, and thus lay outside the path to the future of computers.
Because Mark I used relay technology, it was very slow. It produced results faster than conventional computing methods could but not nearly as fast as machines to be unveiled soon afterward, such as ENIAC. Addition or subtraction required one machine cycle, taking 0.3 seconds. Multiplication required 20 cycles, or 6 seconds, and division could take as much as 51 cycles, or more than 15 seconds. Because of this, in later models division was handled by the multiplication of reciprocals.
Although Mark I was slow, it not only was programmed, rather than being hard-wired for each problem, but was also extremely versatile. Whereas ENIAC was restricted in its original design by the mission of computing ballistic tables, Mark I could accommodate a large variety of programs.
Aiken built three later machines at Harvard. Mark II, like Mark I, used relays as its operating components; Mark III pioneered in using magnetic drum memory and some solidstate elements, along with vacuum tubes. Mark IV had magnetic core memory and was all electronic, using selenium solid-state devices and, later, ones made of germanium.
One of Mark Ill’s unusual features was its automatic coding machine. This unit had a tremendous array of keys corresponding to various subroutines that were stored inside it. If a programmer needed to find the sine of a number, for example, all he or she had to do was to hit the sine key and the whole sine routine would automatically enter in the program. As Grace Hopper recalled, “In other words, Mark III had what today would be called a compiling machine. With this magnificent keyboard you essentially could punch in the program you wanted to run in a form very similar to mathematical notation.” Apparently this was the only such coding machine ever built.
Nevertheless, these machines did not set the pace for the development of computer architecture in the years after World War II. One reason was that Aiken steadfastly opposed the use of a single store for both instructions and data, which became a central feature of post-World War II computers.
What, finally, was Aiken’s importance and influence? It comes down to four principal achievements. First, he demonstrated that it was possible to produce a machine to be programmed to execute a series of commands in a predetermined sequence of operations—without error. The widespread publicity that surrounded the dedication of Mark I gave notice to the world of the dawn of the computer age.
Second, Aiken’s lectures all over the world on the importance of computers and their potential uses were extremely important in gaining support for development of computers. Third, he initiated the application of computers to data processing—not just mathematical problems- including computer billing and accounting, for instance, for electric and gas companies.
Finally, he established at Harvard the world’s first full-fledged graduate program in what is known today as computer science, and it served as a model for programs at other universities. The roster of Aiken’s pupils is astonishing. It includes two of the chief designers of IBM’s System/360 and a number of present and former chairmen of computer science departments. Among others who received their training or apprenticeship under Aiken were Grace Hopper, pioneer of the compiler and certain computer languages; An Wang, founder of the computer company that bore his name; and numerous Europeans who came to spend time working in Aiken’s Harvard Computer Lab and learning the art and science of the computer.
Some historians of the computer believe that this last, the establishment of computer science as a legitimate and recognized part of university curricula and research programs, may have been more important than anything else Aiken did. He opened the curtain on the computer age, and then he filled the stage with some of its greatest players. In so doing, he built a monument more lasting than brass, of longer duration than any single machine. He was a true computer pioneer.