IBM 701

IBM 701

The IBM 701 — the "Defense Calculator" while it was still a secret — was the machine that turned IBM from a tabulating-equipment company into a computer company. Thomas Watson Jr. pushed the project through, Jerrier Haddad and Nathaniel Rochester designed it on the IAS blueprint, and it was announced on 21 May 1952 — IBM's first scientific computer, its first production mainframe, and the founding member of the 700/7000 series that dominated scientific computing until the System/360.^[1]

The sales story is the correction to computing's most famous misquote. The line "I think there is a world market for maybe five computers" — endlessly attributed to Watson Sr. in 1943 — was never said by him. The real remark was Watson Jr.'s, at the 1953 stockholders' meeting, describing the 701's reception: having toured twenty prospective customers expecting orders for five, "we came home with orders for 18." Nineteen systems were eventually installed — the first to IBM's own New York headquarters, eight to aircraft companies, the rest to Los Alamos, Livermore, Lockheed, and the Pentagon, at roughly $12–15,000 a month in rent. The "five computers" quip survives because it was nearly true — it just described a sales forecast, not a worldview.^[2]

Weather, blackjack, and machine translation

The 701's customer list made it the Cold War's scientific workhorse — and its sidelines were the future. In a 1954 Joint Chiefs bake-off against the UNIVAC 1103 for a weather-prediction project, the 701 won unanimously on I/O speed. That January it had also run the Georgetown–IBM experiment — the first public Russian→English machine translation demo. And in 1954 researchers ran millions of simulated blackjack hands on a 701, deriving the optimal play for every card combination — among the first uses of a computer to solve a game by brute statistics.^[3]

The machine itself: 36-bit words, 2,048 words of Williams-tube memory on 72 CRTs, no index registers (the one feature its 1954 successor, the 704, was designed around — along with the industry's move to core memory). And it had cousins: the business-oriented 702, and the 650 — the drum machine that became, by volume, the first mass-produced computer.^[4]

Where it sits

The 701 is where the mainframe industry actually begins — not the first computer, not even the first commercial one (the Ferranti Mark 1 and UNIVAC precede it), but the first product line: Williams-tube memory proven at scale, a sibling strategy (scientific 701, business 702, mass-market 650), and the 700-series throne IBM held until it traded it for the /360.

Check your understanding

• What was the 701's development codename — and who designed it?
• What's the real story behind the "world market for five computers" quote?
• What machine was the 701's design based on?
• What did the 704 add that the 701 lacked?