WILKINSON, James Hardy.

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"An Assessment of the System of Optimum Coding Used on the Pilot Automatic Computing Engine at the National Physical Laboratory." First edition, offprint issue, of this report on improvements in optimum programming made to the Pilot ACE computer, the prototype built from Alan Turing's ACE design. Wilkinson (1919-1986) was Turing's assistant at the National Physical Laboratory and took over the project upon his departure in 1948.Although only built as a prototype, the lack of better technology meant that the Pilot ACE was put into service in 1951. It needed continual improvements, including these on the arrangement of instructions in mercury delay lines. "One problem was that once the machine has finished executing an instruction, the next instruction is certain to still be somewhere in the delay mechanism, and the machine will have to wait until it emerges. It is possible to overcome this problem by including an extra address in each instruction that specifies the location of the next instruction. Rather than storing instructions sequentially in memory, it is possible to store them in locations such that the next one to be executed is just about to exit from the delay line as it is needed... The system resulted in an increase of execution speed of a factor between 2 and 10" (Tomash & Williams).

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