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Volunteers and pioneers in Manchester this week began the painstaking task of rebuilding the world's first stored-program computer in time for its 50th anniversary in June 1998. The Mark 1 prototype, built by a team at Manchester University, marked the beginning of the computer as we know it.

There is more to the long run-up than Mancunian exuberance. Not only does the original machine no longer exist, neither do any detailed designs. In a race against time, volunteers from the Computer Conservation Society, helped by some of the pioneers, will rebuild the machine to run its original program at 11am on June 21 1998, exactly 50 years after its debut.

Chris Burton, the volunteer leading the team of seven, has already proved that it can be done, by building a section of the machine which can store a line of 32 binary digits on a cathode ray tube. But, apart from original published papers, the team will have to rely heavily on carefully preserved laboratory notebooks, contemporary photographs, and the collective recollections of the pioneers. And before they can even begin to reassemble obsolete parts and make them work, they will have to track them down.

ICL, successor to Ferranti Ltd. which commercialised the machine in 1951, is providing workshop facilities, and Manchester University is providing space to build it in. "The Baby" was designed and built by professors Tom Kilburn and the late Freddie Williams, along with Geoff Tootill and Alec Robinson. An ungainly monster by today's standards, it had an all-important feature: 1,024 bits of memory in the shape of charged areas on a cathode ray tube, enough to contain instructions (a program) as well as data. None of them had any inkling of how important such a stored-program digital computer would become.

The reconstructed machine will eventually move to Manchester's Museum of Science and Industry, where computer science students should be able to write their own programs to run it.