The IBM 700 Series

When war broke out on the Korean Peninsula, in June of 1950, IBM CEO Thomas J. Watson Sr. asked America’s political leaders a simple question. How could the company help? Their answer: Build a computer that could tackle time-consuming calculations — like those behind many military operations — in a matter of minutes.

So, on the third floor of a tie factory in Poughkeepsie, New York, an IBM design team started development on what Watson would later refer to as “the most advanced, most flexible high-speed computer in the world” — the Defense Calculator, officially known as the IBM Model 701 Electronic Data Processing Machine.

Some 25 times to 50 times faster than its predecessors, the 701 inaugurated IBM’s 700 series with rapid advancements in computing power, memory capacity and economy of size, making history as the company’s first electronic computer. Unlike IBM’s earlier computing machines, which had been designed with specific functionalities in mind — such as the Selective Sequence Electronic Calculator — the 701 was built as a general purpose device, with the flexibility and capacity to solve previously insurmountable engineering and scientific problems for a broad range of operations. Over the next decade, this first line of IBM business computers, manufactured in bulk for scientific and commercial applications, helped to establish the company as a market leader both in mainframe computers and in the electronics business at large.

According to a press release at the time, the finalized 701 comprised 11 compact and connected units and a trio of electronic storage methods: electrostatic devices called Williams tubes, magnetic drums and magnetic tapes. It was “designed to shatter the time barrier confronting technicians working on vital defense projects,” the release read.

Although the memory capacity of the 701 would pale in comparison to even the most rudimentary laptop computer, it was a marked improvement from earlier data processing machines. The 701’s electrostatic Williams tubes boasted a storage capacity equivalent to 20,000 digits, while the machine’s magnetic drums — cylindrical devices coated in a ferromagnetic material — held as many as 82,920 digits. Its magnetic tapes, similar to those used in home sound recorders at the time, could house 8 million digits per reel.

With significant memory upgrades, the 701 was able to perform more than 16,000 addition or subtraction operations and more than 2,000 multiplication or division operations per second — enabling users to execute complex calculations in just a few minutes. This spawned a wide variety of applications, from aerodynamic measurements to rocket engine designs to studies on the nitrogen molecule for customers ranging from the US Department of Defense to the United States Weather Bureau — the former of which received the very last 701 produced, in 1955.

The 700’s next iteration, the 702, designed particularly for business use, entered the market that same year. For this new machine, IBM pivoted away from a focus on governmental clients to a broader spectrum of customers in the commercial sphere.

Though offering less computational power than the 701, the 702’s speedy input and output functions and its large-capacity electrostatic memory, could, as one Time article put it,“remember enough information to fill a 1,836-page Manhattan telephone book” and “work the information at the rate of 7,200 unerringly logical operations per second.”

Chemists at the agrochemical company Monsanto told Time that the machine could “open up new horizons by rapidly working out complex equations to help discover new products, improve old ones, find out which of dozens of technically ‘correct’ answers to problems are the best.”

Over the next decade, the 700 mainframes continued to feature more optimized memory devices — and faster processing times. With the 704, for instance, the customary Williams tube storage method was replaced by a high-speed magnetic core storage. This machine also introduced to the series floating-point arithmetic and updated software — advancements that would aid the computer in such applications as tracking the US’s first artificial satellite, Vanguard, in 1958.

In the late 1950s, IBM developed the 709 and then the 7090 — which, for the first time, featured transistors instead of vacuum tubes. Though the series was replaced by the release of IBM’s System/360 computers in 1964, the decade of innovation on the 700 machines built the foundation for IBM’s strength in the mainframe computer market.