From Baby to Mark I
From Baby to Mark I
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From Baby to Mark I
Small-Scale Experimental Machine
A Serial Computer

The Manchester Team

Also newly returned to Manchester were Max Newman, I.J. Good and D. Rees - all fresh from the Bletchley Park code-breaking operation and with experience of the Colossus machine.

Newman wanted to set up a computing facility for mathematics and, without knowing about the work on the ENIAC or the proposal to build the ACE, he wrote to Von Neumann at Princeton in order to find out how to build the computer he needed. He then applied to the Royal Society for a grant to build it. The committee formed to consider the application contained one dissenting member who was firmly of the opinion that a second computer project wasn’t worth funding - the NPL ACE would be enough computing power for everyone!

Fortunately the grant was awarded - £20,000 over five years plus £3000 per annum for salaries. Newman used it to create the Royal Society Computing Machine Laboratory.

After spending some time with Von Neumann at the end of 1946, Newman realised that the real difficulty was developing a reliable storage system - one solution was to be found under his nose. 

Small-Scale Experimental Machine

Tom Kilburn joined Williams at Manchester at the start of 1947 and by the end of the year the two of them had a working system that could store 2048 bits. At this point Newman explained to Williams what sort of machine needed to be put with the memory he had created.  They started work at once on a small machine - more or less built around the CRT store. This was called the Small-Scale Experimental Machine (SSEM) but was better known as "Baby“. It made its first successful run of a program on June 21st 1948.



Kilburn and Williams with Baby

In 1988, to mark Baby's 50th anniversary, a replica was built which and is now in  Manchester's Museum of Science and Industry.




The Manchester Baby was a serial computer - that is it worked one bit at a time. When you want to add two eight-bit numbers a serial computer does it by adding the first pair of bits, then the next pair and so on. A serial computer is relatively easy to build but it isn’t the natural way to use the inherently parallel storage provided by the CRT store.

The Baby used 32 words of 32-bit storage and used CRT storage for its accumulator and its control registers. The only input device was a bank of switches and for output you had to read the dots on the front of the CRT tube as binary - there’s direct machine interaction for you!

On June 21, 1948 the first program to run on any stored program computer found the highest factor of an integer. It took 52 minutes and Manchester folklore has it that it was the only program Kilburn ever wrote - the first and his last!

A few words are needed to clarify the position that the Baby holds in the history of computing. The first electronic computer was probably the ENIAC which predated the Baby by two years - but it wasn’t really what we would recognise as a modern computer and more importantly it wasn’t a stored program computer.

To program the ENIAC you had to rewire it. The ENIAC’s team started work on a stored program design immediately and despite working hard they didn’t switch on their machine, the EDVAC,  until late 1950 and it had been beaten to the post not only by the Baby in 1948 but by the Cambridge EDSAC in 1949.



Manchester Mark I


There is a lot of weight behind the claim that the first modern digital computers were British but you have to remember that there was a fairly strong two-way communications channel open between the US and UK pioneers. Kilburn certainly knew of, and fully understood, Von Neumann’s logical design for a stored program computer and the CRT storage system and other Manchester developments were used in US designs.






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