Computing device

Computing devices are a more general class of devices which could perform complicated calculations than 'computers', the meaning of which is generally now 'stored-program computing device' (i.e. the control program is stored in memory that the computer can modify, allowing the program to change itself if it desires). They generally preceded the creation of computers (as defined above); although as Michael Williams observed, "If you add enough adjectives to a description you can always claim [a particular machine to be the 'first']."

Notable early computing devices

Some of the first powerful computing devices were those of Charles Babbage: a prototype of the first, the Difference Engine, was started in the 1820's, but never finished. (The Museum of Science recently built an actual difference engine, using a later design he created, but never attempted to build; it worked reasonably well.) His later proposed Analytical Engine (1870's) was the first programmable computing device, but its program was fixed (in read-only memory, effectively). His engines were all digital, but entirely mechanical.

Vannevar Bush created his Differential Analyzer at MIT in 1928–1931; it was an analog device, mostly mechanical. Many similar machines were then created in the US, UK, Norway, etc.

Howard Aiken, inspired by Babbage's work, began the design of his Automatic Sequence Controlled Calculator in 1937; actually completed and used, it was a large programmable (but not stored program) electro-mechanical digital device. Later successors from IBM were entirely relay-based, not partially mechanical, as the ASCC was, and eventually (in the Selective Sequence Electronic Calculator) partly electronic. Very slightly later than the ASCC, the Bell Telephone Laboratories relay computing devices of George Stibitz were also entirely relay-based, and digital.

At about the same time, in 1938, John Vincent Atanasoff took the next step, and began the creation of the first electronic digital computing device, later called the Atanasoff–Berry Computer. It was not at all programmable; it could only solve systems of simultaneous equations. It was notable for having inspired John Mauchly when he later set out to build the ENIAC; and also for being the first digital electronic computing device to use capacitor-based memory - an approach to memory now ubiquitous in the Dynamic RAM of all modern computers.

The Colossus digital electronic code-breaking devices of Tommy Flowers, built in the UK during World War Two (construction of the first one started in 1943), were notable because they showed that large electronic computing devices could be made to operate reliably, because quite a few were produced, and because many of the post-War computer pioneers in the UK learned about the suitability of electronics for digital computing devices from them. They are often described as 'programmable', but this is incorrect - they had no program of any form; a better description is 'configurable'.

Effectively the last step before true computers was the ENIAC, a large digital electronic computing device. As originally designed, it was only configurable, requiring considerable effort to re-configure it to perform a different computation. In 1947 an effort was started to re-configure it in a way that added a certain amount of programmability, via a program stored in the 'function-table switches' (originally intended as a ROM data source). Later, minor hardware modifications improved ENIACs efficiency when configured as a stored-program machine; it started to operate in that mode in 1948.

Further reading

• Editor - Brian Randell, The Origins of Digital Computers: Selected Papers, Springer-Verlag, Berlin, Heidelberg, New York, 1973, 1982 (3rd edition)
• Editors - Nicholas Metropolis, Jack Howlett, Gian-Carlo Rota, A History of Computing in the Twentieth Century, Academic Press, New York, 1980
• Editors - Raúl Rojas, Ulf Hashagen, The First Computers: History and Architectures, MIT Press, Cambridge, 2002

External links

• Disambiguating the first computer
• Colossus computer - a good and detailed description