page_title: Manchester Baby
section_title: First programs
hierarchical_section_title: Manchester Baby / Programming / First programs
caption_attribution_description: English: Photograph of the Monitor and Control 'Node' of the replica SSEM. The CRT in this image is used as the output device, and the red switches near the bottom left of the photo are used as the input device.
context_page_description: The Manchester Baby, also called the Small-Scale Experimental Machine, was the first electronic stored-program computer, was built at the University of Manchester, UK, by Frederic C. Williams, Tom Kilburn, and Geoff Tootill, and ran its first program on 21 June 1948.
  The machine was not intended to be a practical computer, but was instead designed as a testbed for the Williams tube, the first truly random-access memory. Although considered "small and primitive" even by the standards of its own time, it was nonetheless the first working machine to contain all the elements essential to a modern electronic computer. As soon as the Baby had demonstrated the feasibility of its design, a project was initiated at the university to develop it into a more usable computer, the Manchester Mark 1. The Mark 1 in turn quickly became the prototype for the Ferranti Mark 1, the world's first commercially available general-purpose computer.
  The Baby had a 32-bit word length and a memory of 32 words.
context_section_description: Three programs were written for the computer. The first, consisting of 17 instructions, was written by Kilburn, and so far as can be ascertained first ran on 21 June 1948. It was designed to find the highest proper factor of 2¹⁸ (262,144) by trying every integer from 2¹⁸ − 1 downwards. The divisions were implemented by repeated subtractions of the divisor. The Baby took 3.5 million operations and 52 minutes to produce the answer (131,072). The program used eight words of working storage in addition to its 17 words of instructions, giving a program size of 25 words.
  Geoff Tootill wrote an amended version of the program the following month, and in mid-July Alan Turing — who had been appointed as a reader in the mathematics department at Manchester University in September 1948 — submitted the third program, to carry out long division. Turing had by then been appointed to the nominal post of Deputy Director of the Computing Machine Laboratory at the university, although the laboratory did not become a physical reality until 1951.
caption: Output CRT
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