The Ferranti Mark 1: World’s First Commercially Available General-Purpose Computer

It stored data in cathode-ray tubes and a rotating magnetic drum


The Ferranti Mark 1 was the first commercially available general-purpose computer. The one shown in this 1955 photo—a slightly improved model known as the Ferranti Mark 1*—was used to help forecast election results, calculate wages, and produce actuarial tables, among other things.

Based on the Manchester Mark 1 and built by Ferranti Ltd., the huge machine was housed in two spacious bays, each 5 meters long, 2.4 meters high, and 1 meter wide, with a control desk at one end. Inside were 4,000 electronic valves (or vacuum tubes), 2,500 capacitors, 15,000 resistors, and nearly 10 kilometers of wiring. It consumed 27 kilowatts of power and operated at a base clock frequency of 100 kilohertz.

The Ferranti Mark 1’s unique memory system (part of which is shown above) could store just over a kilobyte of data in cathode-ray tubes for high-speed access; a rotating magnetic drum offered 82 kilobytes of permanent storage. The mathematician Mary Lee Berners-Lee recounted the trials of programming a Ferranti Mark 1 in a 2001 oral history: “[W]hat you could do on that machine was make it go through one instruction at a time, and watch actually what was happening on the cathode-ray tubes. But that, of course, took a lot of computer time, and you would have people in the queue waiting to use the computer behind you. There was a big notice over the computer—I think it was [a play on the one] devised by IBM—which said, ‘Think—but not here!’ ” [For more details about the programming, see Brian Napper’s account here.]

In 1948, Alan Turing and David Champernowne devised a set of rules for a chess program called Turochamp, which Turing had started to code for the University of Manchester’s Ferranti Mark 1 before his untimely death. In a game against colleague Alick Glennie, Turing worked through the Turochamp algorithm by hand, which took him half an hour per move. The game reportedly lasted several weeks, and Turochamp lost in 29 moves.

As for what the fellow is doing in this photo, or who he is, we don’t know. We invite readers to tell us.

This article appears in the May 2016 print issue as “Listening for Gremlins.”

Part of a continuing series looking at old photographs that embrace the boundless potential of technology, with unintentionally hilarious effect.