Celebrating the first electronic computer

Around 11am on 21 June 1948, engineers at the University of Manchester switched on a brand new kind of machine. And 52 minutes later, the machine (nicknamed 'Baby') successfully produced a pattern of glowing phosphor dots on a special cathode ray tube.

Baby was a revolutionary new kind of computer. In 1948, computers were primitive devices that required weeks of rewiring to run a new program. In contrast, Baby's operator simply entered each new program into its memory using a bank of dedicated switches and ran it before reading off the result.

Frederic Williams, Geoff Tootill and Tom Kilburn built Baby as a test bed for Williams' new cathode ray tube storage device. Baby used these glowing devices as registers in the CPU and to store 32 instructions and 32 data items. The CPU understood just six different instructions and ran at 100KHz.

Being able to simply enter programs instead of rewiring the entire machine changed everything, as a BBC newsreel report of the time explained: "Anyone who urgently wishes to know whether 2127-1 is a prime number or not can be given the answer by an electronic brain in under twenty-five minutes instead of by a human brain in six months," it gushed.

Baby's 60th birthday

To mark the 60th anniversary of the original team's efforts, a crew of volunteers led by Chris Burton has built a working replica of Baby reflecting the state of the original hardware at the time it ran the first stored program. Sited on the ground floor of the main building at Manchester's Museum of Science and Industry, it runs for visitors every Tuesday between 12pm and 2pm. Entrance is free.

As part of the birthday celebrations, Professor Steve Furber of the Advanced Processor Technologies Group at the University of Manchester delivered 2008's annual Kilburn lecture on the subject of Baby's development.

"The Baby filled a medium sized room," he says. "It used about 3.5KW of electrical power and it executed 700 instructions per second with those 3.5KW. If you take a modern, efficient processor such as the ARM968, it occupies the order of a square millimetre of silicon. It uses about 20mW of electrical power and it executes 200 million instructions per second."

Banging the magnetic drum

The UK government asked Manchester-based Ferranti to help develop the machine further. The resulting Manchester Mk 1 computer of 1949 was surprisingly modern – using magnetic drums to store programs – and it quickly became the commercial Ferranti Mk 1. The first model rolled off the production line for delivery to the university in February 1951.

The intervening years have seen the capabilities of stored program computers develop at an unimaginable pace. "If the car industry had improved as much over this time," adds Furber, "then one litre of oil would keep the whole UK happy for a year."