Technology correspondent Christine McGourty examines the invention that changed the world (Dur 4'44")

A replica of the first computer capable of storing a programme has been built, 50 years after the original pointed the way to the future.

Scientists at Manchester University beat America in the technology race when they unveiled Manchester Mark 1, otherwise known as The Baby.

It was just a jumble of wires and switches to the untrained eye and had little of the compactness of today's computers.

The Baby had a random access memory of just 32 locations, giving a grand total memory capacity of 1,024 bits - tiny by today's standards. But crucially it was the first device to be able to hold a stored programme.

The Baby gave birth to the computer age

This made it the direct ancestor of today's computers and the replica has been built to celebrate the anniversary. The original machine was dismantled in the 1950s.

As a young man, Tom Kilburn wrote the first computer programme and keyed it in himself. Now as Professor Kilburn, he has been helping to build the replica, but says nothing can quite match that "Eureka" moment when it first worked perfectly.

Prof Tom Kilburn

He said: "After about an hour we fed the programme in and it worked very successfully and we saw the digits flashing on the cathode ray tube monitor. We cheered like mad. It was a wonderful moment, never to be repeated."

Engineer Chris Burton has spent three years building the 1997 version of the machine, having pieced it together from photographs and using the original techniques.

He said: "The original Baby machine which operated in 1948 was very important because it was the world's first computer which would hold a stored programme and as such it was the forerunner of all modern computers which we know today.

"All of them can trace their ancestry back to that Baby machine in 1948."

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