Williams and Kilburn built the Small-Scale Experimental Machine at Manchester University as the smallest practicable computer to check out the CRT store later to become known as the “Williams Tube” store (see also here).

Further development and additions to the SSEM led to a machine suitable for productive computing, referred to as the Manchester University Mark I, from mid-1949 onwards. In turn, this was developed and engineered by Ferranti Ltd to become the Ferranti Mark I and Mark I* computers. A number of differences to the instruction repertoire, a much larger store and (perhaps most significantly) the introduction of a modifier register differentiate this machine from the original.

The Mark I

• Was the first computer to be commercially sold (1950 to MU, then to Toronto University 1951), ahead of UNIVAC
• Pioneered system software written by Alan Turing (1951): a proto Operating System with system calls and command processor.
• Pionered compiler development: Glennie Autocode (1952) and Brooker Autocode (1954)
• Pioneered video games and digital art: Draughts program and Love Letters program by Christopher Strachey (1952)

32 64	s_m1sim.zip containing an emulator by Andy Molyneux of Manchester University. This was on public display at the press launch of the SSEM Rebuild Project, 5th March 1996.
	Roberto Sancho Villa’s mark I emulator from GitHub. There is a useful readme file included in the base level of the download. The SimH based Mark I emulator includes all the historical programs listed above, recovered from original surviving documents. You can play Draughts, run already made sample programs and create and compile your own Autocode programs. Read the included MarkI_ReadMe.txt included in zip file for installation and usage instructions. The emulator features a fully functional graphical Control Panel, that allows to interact with the machine the realistic (and hard) way as in the good old days. A set of already made batch files allows to start programs on the easy way, and just enjoy the blinkenlights and i/o device animations.