Manchester Baby

Manchester Baby
	Replica of the Baby at the Science and Industry Museum in Castlefield, Manchester
Also known as	Small-Scale Experimental Machine
Developer	Frederic Calland Williams; Tom Kilburn; Geoff Tootill
Product family	Manchester computers
Release date	21 June 1948
Memory	1 kibibit (1,024 bits)
Successor	Manchester Mark 1

The Manchester Baby, also called the Small-Scale Experimental Machine (SSEM),^[1] was the first electronic stored-program computer. It was built at the University of Manchester by Frederic C. Williams, Tom Kilburn, and Geoff Tootill, and ran its first program on 21 June 1948.^[2]

The Baby was not intended to be a practical computing engine, but was instead designed as a testbed for the Williams tube, the first truly random-access memory. Described as "small and primitive" 50 years after its creation, it was the first working machine to contain all the elements essential to a modern electronic digital computer.^[3] As soon as the Baby had demonstrated the feasibility of its design, a project was initiated at the university to develop it into a full scale operational machine, 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.^[4]^[5]

The Baby had a 32-bit word length and a memory of 32 words (1 kibibit, 1,024 bits). As it was designed to be the simplest possible stored-program computer, the only arithmetic operations implemented in hardware were subtraction and negation; other arithmetic operations were implemented in software. The first of three programs written for the machine calculated the highest proper divisor of 2¹⁸ (262,144), by testing every integer from 2¹⁸ downwards. This algorithm would take a long time to execute—and so prove the computer's reliability, as division was implemented by repeated subtraction of the divisor. The program consisted of 17 instructions and ran for about 52 minutes before reaching the correct answer of 131,072, after the Baby had performed about 3.5 million operations (for an effective CPU speed of about 1100 instructions per second).^[2]

^ Burton, Christopher P. (2005). "Replicating the Manchester Baby: Motives, methods, and messages from the past". IEEE Annals of the History of Computing. 27 (3): 44–60. doi:10.1109/MAHC.2005.42. S2CID 1852170.
^ ^a ^b Enticknap, Nicholas (Summer 1998), "Computing's Golden Jubilee", Resurrection (20), The Computer Conservation Society, ISSN 0958-7403, archived from the original on 9 January 2012, retrieved 19 April 2008
^ Cite error: The named reference EarlyComputers was invoked but never defined (see the help page).
^ Napper, R. B. E., Introduction to the Mark 1, The University of Manchester, archived from the original on 26 October 2008, retrieved 4 November 2008
^ Briggs, Helen (21 June 2018). "The 'Baby' that ushered in modern computer age". BBC. Retrieved 21 June 2018.

[1] Burton, Christopher P. (2005). "Replicating the Manchester Baby: Motives, methods, and messages from the past". IEEE Annals of the History of Computing. 27 (3): 44–60. doi:10.1109/MAHC.2005.42. S2CID 1852170.

[Resurrection-2] Enticknap, Nicholas (Summer 1998), "Computing's Golden Jubilee", Resurrection (20), The Computer Conservation Society, ISSN 0958-7403, archived from the original on 9 January 2012, retrieved 19 April 2008

[EarlyComputers-3] Cite error: The named reference EarlyComputers was invoked but never defined (see the help page).

[NapperMK1-4] Napper, R. B. E., Introduction to the Mark 1, The University of Manchester, archived from the original on 26 October 2008, retrieved 4 November 2008

[The_'Baby'_that_ushered_in_modern_computer_age-5] Briggs, Helen (21 June 2018). "The 'Baby' that ushered in modern computer age". BBC. Retrieved 21 June 2018.

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