Assessment System Optimum Coding Used by Wilkinson James (2 results)

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). Tomash & Williams W76. Quarto, pp. 32. Diagrams. Original light green printed wrappers. Wrappers lightly soiled and creased, head of spine starting: in very good condition.

Wilkinson, James Hardy (1919-86). An assessment of the system of optimum coding used on the pilot Automatic Computing Engine at the National Physical Laboratory. Offprint from Philosophical Transactions of the Royal Society of London, Series A: Mathematical and physical sciences, 248 (1955). 253-281pp. Text diagrams. 302 x 236 mm. Original printed wrappers, label partly removed from front wrapper, ownership signature in upper corner of front wrapper. Fine. Bookplate of Erwin Tomash. First Edition, Offprint Issue. The National Physical Laboratory's ACE (Automatic Computing Engine) was designed by Alan Turing, who began working on the project a few months before he joined the NPL's mathematics division on October 1, 1945. Construction of the ACE began with a "test assembly" to try out Turing's ideas of computer design; after Turing's departure from the NPL in September 1947, this project was taken over by his assistants, James H. Wilkinson and Michael Woodger. In early 1949 the original ACE test assembly was abandoned and a new version, redesigned to make the electronics as simple as possible, began construction in early 1949. This machine, completed in 1950, came to be known as the "Pilot ACE." The Pilot ACE, although intended as a prototype, was immediately pressed into service, as it was then the only computer in a British government department. It remained in operation until 1956, undergoing several modifications during its lifetime. The present report "describes the system of optimum coding which is used on the Pilot ACE . . . It includes a number of simple examples of programs prepared for the machine and gives an assessment of the gain in speed which results from the use of optimum coding in general. It concludes with a description of the design of the full-scale ACE which takes full advantage of the general principles embodied in the design of the Pilot ACE" (p. 253). .