A Brief History of Computing
- First Generation Computers

© Copyright 1996-2005, Stephen White

(Click here to return to the History Homepage)

1943 - January

The Harvard Mark I (originally ASCC Mark I, Harvard-IBM Automatic Sequence Controlled Calculator) was built at Harvard University by Howard H. Aiken (1900-1973) and his team, partly financed by IBM - it became the first program controlled calculator. The whole machine is 51 feet long, weighs 5 tons, and incorporates 750,000 parts. It used 3304 electromechanical relays as on-off switches, had 72 accumulators (each with its own arithmetic unit) as well as mechanical register with a capacity of 23 digits plus sign. The arithmetic is fixed-point, with a plugboard setting determining the number of decimal places. I/O facilities include card readers, a card punch, paper tape readers, and typewriters. There are 60 sets of rotary switches, each of which can be used as a constant register - sort of mechanical read-only memory. The program is read from one paper tape; data can be read from the other tapes, or the card readers, or from the constant registers. Conditional jumps are not available. However, in later years the machine is modified to support multiple paper tape readers for the program, with the transfer from one to another being conditional, sort of like a conditional subroutine call. Another addition allows the provision of plugboard-wired subroutines callable from the tape.

Used to create ballistics tables for the US Navy.

1943 - December The earliest Programmable Electronic Computer first ran (in Britain), it contained 2400 Vacuum tubes for logic, and was called the Colossus. It was built, by Dr Thomas Flowers at The Post Office Research Laboratories in London, to crack the German Lorenz (SZ42) Cipher used by the 'Enigma' machines. Colossus was used at Bletchly Park during WWII - as a successor to April's 'Robinson's. It translated an amazing 5000 characters a second, and used punched tape for input. Although 10 were eventually built, unfortunately they were destroyed immediately after they had finished their work - it was so advanced that there was to be no possibility of its design falling into the wrong hands (presumably the Russians). One of the early engineers wrote an emulation on an early Pentium - that ran at 1/2 the rate!
1946 ENIAC (Electronic Numerical Integrator and Computer): One of the first totally electronic, valve driven, digital, computers. Development started in 1943 and finished in 1946, at the Ballistic Research Laboratory, USA, by John W. Mauchly and J. Presper Eckert. It weighed 30 tonnes and contained 18,000 Electronic Valves, consuming around 25kW of electrical power - widely recognised as the first Universal Electronic Computer. It could do around 100,000 calculations a second. It was used for calculating Ballistic trajectories and testing theories behind the Hydrogen bomb.
1948 - June 21

SSEM, Small Scale Experimental Machine or 'Baby' was built at Manchester University (UK), It ran its first program on this date. Based on ideas from Jon von Neumann (a Hungarian Mathematician) about stored program computers, it was the first computer to store both its programs and data in RAM, as modern computers so.

By 1949 the 'Baby' had grown, and aquired a magentic drum for more perminant storage, and it became the Manchester Mark I. The Ferranti MArk I was basically the same as the Manchester Mark I but faster and made for commmercial sale.

1949 - May 6 Wilkes and a team at Cambridge University build a stored program computer - EDSAC. It used paper tape I/O, and was the first stored-program computer to operate a regular computing service.
1949 EDVAC (electronic discrete variable computer) - First computer to use Magnetic Tape. This was a breakthrough as previous computers had to be re-programmed by re-wiring them whereas EDVAC could have new programs loaded off of the tape. Proposed by John von Neumann, it was completed in 1952 at the Institute for Advance Study, Princeton, USA.
1951 Whirlwind, the first real-time computer was built for the US Air Defence System.
1951 UNIVAC-1. The first commercially sucessful electronic computer, UNIVAC I, was also the first general purpose computer - designed to handle both numeric and textual information. Designed by J. Presper Eckert and John Mauchly, whose corporation subsequently passed to Remington Rand. The implementation of this machine marked the real beginning of the computer era. Remington Rand delivered the first UNIVAC machine to the U.S. Bureau of Census in 1951. This machine used magentic tape for input.
1952 EDVAC (Electronic Discrete Variable Computer) completed at the Institute for Advanced Study, Princeton, USA (by Von Neumann and others).

© Copyright 1996-2004, Stephen White My homepage - email:swhite@ox.compsoc.net