It has been 75 years since the first Ferranti Mark I, the world’s first commercially available general-purpose computer, was delivered to the University of Manchester on 12 February 1951.
It was to be the fruition of a government contract with Ferranti Ltd, signed in 1948 to make a production version of the recently built Manchester Mark I to ‘Professor Williams’ specifications’, referring to computer pioneer Sir Frederic Williams.
Based on its predecessor, the Ferranti Mark I had a larger memory, faster multiplier and more instructions for programmers. The University of Manchester was the first to receive one of nine machines built between 1951 and 1957.
The Ferranti Mark 1 used the Williams tube – or Williams-Kilburn tube to acknowledge fellow pioneer Tom Kilburn – the first digital storage device. The computer memory enabled bits of data to be stored on the charged screen of a cathode ray tube.
First machine to have random access memory
According to Computer Historian, Simon Lavington, (1939-2025) the Ferranti Mark I: “Was the first machine on the market to have a random access memory.”
In his article, published in 2020 by the BCS, The Chartered Institute for IT, he goes on to say that: “This was at a time when most of the prototype computers had sequential main memories. Random access is to be desired from the perspective of performance and ease of programming.
“The Mark I also contained index registers – these are now part of every computer. So, it was potentially easier to program than many others.”
Advancing industry
In its early years the Ferranti Mark I’s calculating capabilities were used by the UK government in its defence industry and also civil engineering projects such as by the University of Toronto, which used it to calculate a system of canals and dams in Canada.
From 1951 to 1953, enhancements were made to the computer, with later versions know as Mark I*. In our Archive we have a document written by Joan Smith, who was employed by British aircraft manufacturer Avro in 1956 to work on the Ferranti Mark I*, which the company had bought two years earlier.
Large-scale scientific machine
“I was employed by Avro to work with the Ferranti Mark I*, described as a large-scale scientific machine for calculations, on the Vulcan [bomber] aircraft,” she said.
“The machine generated 8kW of heat which necessitated a refrigeration unit, also used by the engineers on occasions to cool drinks.
“It was housed in a purpose-built room of which the walls were screened by copper mesh to avoid interference with the bits (binary digits) stored on the face of the cathode ray tubes. Power obtained directly from the local power station at Chadderton to protect it from power cuts and fluctuations of power.”
Solving problems
Avro used the Mark I* for ten years to solve problems associated with aircraft design, management, and programmable machine tools.
“Everything possible was done to provide the company’s considerable investment with a near-perfect operating environment. However good the hardware, it was the uses to which it was put by means of software that would allow the computer to pay its way, at the same time advancing the aircraft industry, enabling it to produce results faster and more accurately.
Smith noted that the cost of a Mark 1* to a customer was recorded as being £83,000, £100,000 if sent abroad.
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