The modern computer age began 70 years ago today

Manchester Baby, the first stored-program computer, ran its first programme on this day in 1948

By Becky Cunningham, last updated Jun 21, 2018.


  1. Becky
    It's difficult to imagine life without computers, and weirder still to imagine that the first computers were being tested just 20 years after sliced bread became available. On this day in 1948, at around 11am, the Manchester Baby ran its first programme. It took 52 minutes to complete the task, during which time it performed 3.5 million calculations.

    SSEM_Manchester_museum_close_up.jpg

    The Manchester Baby, also known as the Small-Scale Experimental Machine (SSEM), was the world's first stored-program computer (ie the programme was stored in electronic memory as opposed to plugboards or other mechanisms). It was built at Victoria University of Manchester in the UK by Frederic C. Williams, Tom Kilburn, and Geoff Tootill.

    The computer was designed to test the Williams Tube, the first random-access storage device. The work quickly lead to the development of the Manchester Mark 1, which in turn became a prototype for the world's first commercially available computer - the Ferranti Mark 1.

    manchester baby circuit diagram.jpg
    Circuit diagram for SSEM (CI = Control Instruction, PI = Present Instruction)


    Some facts about Manchester Baby:
    • It had a 32-bit word length and a memory of 32 words (1024 bits)
    • An effective CPU speed of 1,000 instructions per second (IPS)
    • Seven different types of instruction could be input
    • Programmes were loaded using a push button typewriter
    • Based on concepts by John von Neumann and Alan Turing
    • 5.23m long, 2.26m tall, weighed nearly 1 ton
    • Contained 550 vacuum tubes, 300 diodes, and 250 pentodes
    • Power consumption: 3500W
    • Clock rate: 100kHz
    You can view a replica of the Manchester Baby at the Museum of Science and Industry in Manchester.