Background
By the late 1940s, IBM was a major maker of office machines, especially punched-card tabulating equipment. It had also worked on large calculators such as the Harvard Mark I and had built some electronic calculating equipment of its own. But it had not yet released a general-purpose, stored-program electronic computer for customers. Competitors, including the company formed by Eckert and Mauchly, were moving ahead.
The Korean War, which began in 1950, added urgency. Defense-related organizations needed heavy calculation, and IBM, partly in response, started a project to design a large scientific computer. The project was known inside the company as the Defense Calculator, and it was announced publicly in 1952 under the name IBM 701.
What the machine was
The IBM 701 was a large, vacuum tube computer meant mainly for science and engineering. A few of its characteristics are well documented, although specifics vary by source:
- It was a binary, stored-program machine, in contrast with the decimal design of ENIAC.
- Its main memory used Williams tubes, a form of storage that kept bits as patterns of electric charge on the face of a cathode-ray tube. This was fast but sometimes unreliable, and it was later replaced in IBM’s designs by magnetic core memory.
- It used magnetic tape for larger storage and punched cards for input and output, along with printed output.
- It was rented to customers rather than sold outright, which was IBM’s usual business model for its equipment.
Programs were written in machine code or in assembly-like notations at first. Higher-level languages arrived for later IBM machines, notably FORTRAN, which was developed for the 704 that followed.
Who used it
Only a small number were built. A figure of around 19 is frequently cited, although sources should be checked if exact numbers matter. The first was installed at IBM’s own headquarters in New York in late 1952, and others went to customers over the following couple of years.
Those customers were mainly organizations that needed serious computing power: government and defense laboratories, aircraft and aerospace manufacturers, and a few research groups. The sort of work it did included aircraft design calculations, nuclear weapons research and other forms of scientific computing. Some users also experimented with early programs in areas such as games and numerical weather methods, as with other machines of the period, though accounts of individual firsts are often disputed.
Why it mattered
The 701 was not the first electronic computer, nor the first sold to customers. The Ferranti and UNIVAC machines were already on the market or about to be. Its importance lies elsewhere.
It brought IBM in. IBM was a large and well-established company with a sales force, service organization and customer relationships. Its decision to commit to electronic computers made the field look more serious, and its resources soon turned it into the leading supplier of mainframe computers.
It trained a generation. The people who programmed and operated 701s learned lessons about reliability, debugging and shared software. Users of IBM’s scientific machines formed an association, SHARE, in the mid-1950s to exchange programs and ideas. This was an early example of a user community, and it set a pattern later seen with other platforms.
It led to successors. The 701 was followed by the business-oriented IBM 702 and the improved scientific IBM 704, which used magnetic core memory and had hardware support for floating-point arithmetic. The more affordable IBM 650 then reached many more customers. Together these machines carried IBM from the laboratory-oriented start to a wider market.
The step toward commercial computing
It is tempting to treat the 701 as a purely scientific machine on a separate track from business computing, but the boundary was blurry. Companies and agencies used the same basic technology for commercial work, and IBM’s experience building and servicing the 701 fed into products aimed at business customers. The company’s later commercial success rested on that accumulated knowledge as well as on its existing customer base. The wider move from laboratory to office is covered in the story of the first commercial computers, while the machines of the decade as a whole are surveyed in 1950s computers.
Keeping it in proportion
Early computer histories can make any single machine look decisive. The 701 was one product in a crowded field, built by a team within a company drawing on ideas that had been circulating in universities and government laboratories for several years. Some details of its development, including exact dates of design decisions and how much influence particular people had, are still discussed. What can be said with reasonable confidence is that it marked IBM’s serious entry into electronic computing in the early 1950s and that the company’s later dominance grew out of the decisions made in that period.