Design and Operation
Colossus used state-of-the-art vacuum tubes (thermionic valves), thyratrons and photomultipliers to optically read a paper tape and then applied a programmable logical function to every character, counting how often this function returned "true". Although machines with many valves were known to have high failure rates, it was recognised that valve failures occurred most frequently with the current surge when powering up, so the Colossus machines, once turned on, were never powered down unless they malfunctioned.
Colossus was the first of the electronic digital machines with programmability, albeit limited by modern standards:
- it had no internally stored programs. To set it up for a new task, the operator had to set up plugs and switches to alter the wiring.
- Colossus was not a general-purpose machine, being designed for a specific cryptanalytic task involving counting and Boolean operations.
It was thus not a fully general Turing-complete computer, even though Alan Turing worked at Bletchley Park. It was not then realized that Turing completeness was significant; most of the other pioneering modern computing machines were also not Turing complete (e.g. the Atanasoff–Berry Computer, the Bell Labs relay machines (by George Stibitz et al.), or the first designs of Konrad Zuse). The notion of a computer as a general purpose machine—that is, as more than a calculator devoted to solving difficult but specific problems—did not become prominent for several years.
Colossus was preceded by several computers, many of them first in some category. Zuse's Z3 was the first functional fully program-controlled computer, and was based on electromechanical relays, as were the (less advanced) Bell Labs machines of the late 1930s (George Stibitz, et al.). The Atanasoff–Berry Computer was electronic and binary (digital) but not programmable. Assorted analog computers were semiprogrammable; some of these much predated the 1930s (e.g., Vannevar Bush). Babbage's Analytical engine design predated all these (in the mid-19th century), it was a decimal, programmable, entirely mechanical construction—but was only partially built and never functioned during Babbage's lifetime (the first complete mechanical Difference engine No. 2, built in 1991, does work however). Colossus was the first combining digital, (partially) programmable, and electronic. The first fully programmable digital electronic computer was the ENIAC which was completed in 1946.
Read more about this topic: Colossus Computer
Famous quotes containing the words design and/or operation:
“If I knew for a certainty that a man was coming to my house with the conscious design of doing me good, I should run for my life ... for fear that I should get some of his good done to me,some of its virus mingled with my blood.”
—Henry David Thoreau (18171862)
“It requires a surgical operation to get a joke well into a Scotch understanding. The only idea of wit, or rather that inferior variety of the electric talent which prevails occasionally in the North, and which, under the name of Wut, is so infinitely distressing to people of good taste, is laughing immoderately at stated intervals.”
—Sydney Smith (17711845)