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Computer Pioneer Geoff Tootill Passed Away (theguardian.com)

Posted by EditorDavid on from the living-for-almost-a-century dept.

"Computer pioneer Geoff Tootill passed away in October," writes long-time Slashdot reader tigersha. Born in 1922, Tootill began his career troubleshooting airborne radar systems during World War II, leading him to some pioneering research in the late 1940s. "He worked on the first computer that stored a program in main memory, as opposed to a paper tape, and actually had the opportunity to teach Alan Turing and debug one of Turing's programs." The Guardian remembers: The computer could store just 32 instructions or numbers using a single cathode ray tube. The machine first worked in June 1948, taking 52 minutes to find the highest factor of 262,144, involving about 3.5 million arithmetic operations. The following year, Tootill transferred to Ferranti, the Manchester-based electrical engineering company, to specify a full-scale computer...the world's first commercially available computer.
That was the Ferranti Mark I, first released in 1951.

Tootill passed away at the age of 95.

5 of 36 comments (clear)

  1. Farewell by Anonymous Coward · · Score: 2, Insightful

    Farewell Sir, and thank you for everything that you helped create.

  2. In modern terms by fahrbot-bot · · Score: 3, Informative

    The computer could store just 32 instructions or numbers using a single cathode ray tube.

    About the same as our average current politician.

    The machine first worked in June 1948, ...

    [ see above ]

    --
    It must have been something you assimilated. . . .
  3. highest factor of 262,144 by ortholattice · · Score: 2

    FTA: "52 minutes to find the highest factor of 262,144, involving about 3.5 million arithmetic operations"

    I wonder what algorithm they were using. 262144=2^18, so the highest (prime) factor is 2, and almost any algorithm (such as the sieve of Eratosthenes) would try 2 first.

    1. Re:highest factor of 262,144 by daveime · · Score: 3, Interesting

      I wondered this also. I'm guessing at that time, they perhaps didn't have MUL or DIV instructions, or even the concept of SHL or ROL which would have allowed a test for "divisible by 2".

      So I'm guessing they started with a "factor", example 2, added it together repeatedly until it equalled or was greater than the target, remembering how many additions were made. If equal to the target, repeat the addition half the number of times, and replace that with the old target, and output 2 as a factor. If greater than the target, try the next "factor" 3,5,7 etc etc.

      Repeat until target = 0

      It's surprising how relatively recent native MUL and DIV operations are in processors.

    2. Re:highest factor of 262,144 by Anonymous Coward · · Score: 4, Informative

      From the Wikipedia article on the computer (the "Manchester Small-Scale Experimental Machine", aka "Baby"):

      The first of three programs written for the machine found the highest proper divisor of 2^18 (262,144), a calculation that was known would take a long time to run—and so prove the computer's reliability—by testing every integer from 2^18 1 downwards, as division was implemented by repeated subtraction of the divisor. The program consisted of 17 instructions and ran for 52 minutes before reaching the correct answer of 131,072, after the SSEM had performed 3.5 million operations (for an effective CPU speed of 1.1 kIPS).