In 1936, mathematician Alan Turing published a definition of a theoretical "universal computing machine", a computer which held its program on tape, along with the data being worked on. Turing proved that such a machine was capable of solving any conceivable mathematical problem for which an algorithm could be written. During the 1940s, Turing and others such as Konrad Zuse developed the idea of using the computer's own memory to hold both the program and data, instead of tape, but it was mathematician John von Neumann who became widely credited with defining that stored-program computer architecture, on which the Manchester Mark 1 was based.
The practical construction of a von Neumann computer depended on the availability of a suitable memory device. The University of Manchester's Small-Scale Experimental Machine (SSEM), the world's first stored-program computer, had successfully demonstrated the practicality of the stored-program approach and of the Williams tube, an early form of computer memory based on a standard cathode ray tube (CRT), by running its first program in June 1948. Early electronic computers were generally programmed by being rewired, or via plugs and patch panels; there was no separate program stored in memory, as in a modern computer. It could take several days to reprogram ENIAC, for instance. Stored-program computers were also being developed by other researchers, notably the National Physical Laboratory's Pilot ACE, Cambridge University's EDSAC, and US Army's EDVAC. The SSEM and the Mark 1 differed primarily in their use of Williams tubes as memory devices, instead of mercury delay lines.
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