Tag Archives: Computing

The Pegasus Computer

Volunteer Chris Burton reflects on helping maintain and run Pegasus, one of the oldest computers in the world. Chris is a member of the Computer Conservation Society. 

Surrounded by paper tape readers, paper tape punch and teleprinter, I am in control of an early electronic computer named Pegasus. The imposing array of switches, lights, knobs and display screens, gives me command of a powerful yet responsive machine. There is a lot of noise from the cooling air blowers, and occasionally the machine emits strange sounds from its loudspeaker indicating the progress of an application program. This is how the original operators of Pegasus would have felt in the 1950s.


Sometimes an operator would be the person who actually designed and wrote the program, taking hands-on control to ensure the program worked correctly. Operators became wizards at manipulating the control switches to direct what the machine does, as well as monitoring the binary data shown on the cathode ray tube screens. While the program was running, they rolled-up any punched-paper tapes to be kept, or glanced up at the clock to write the next log-book entry. There was a pervading feeling of warmth, comfort and order.

The Ferranti Pegasus computer was developed in the early 1950s by a team of former Elliott Brothers Ltd engineers using a technology pioneered in the Elliott/NRDC 401 computer. The engineering of Pegasus is outstanding. It is assembled from hundreds of plug-in electronic modules (see below) about the size of a paper-back book which contain two or three valves (vacuum tubes – pre-dating the use of transistors or microprocessors)

Some of these modules are used as the internal memory of the computer but the main memory is based on magnetised spots on the surface of a rotating drum, similar to a modern day magnetic disc drive. Data input and output is via 5-track punched-paper tape. No typewriter keyboard or display screen!

Ferranti Pegasus computer circuit boards, 1956. © Science Museum / SSPL

Ferranti Pegasus computer circuit boards, 1956. © Science Museum / SSPL

Pegasus was the first “user friendly” computer, and about forty Pegasus systems were sold, between 1956 and 1962. Scores of programmers and users of the machine have commented on the ease of programming and operation. A fundamental part of Pegasus was a simple operating system, a set of routines called Initial Orders which was stored permanently in a write-protected area of the drum. Pressing the “Start” key caused the Initial Orders to be executed, and they gave the programmer facilities for inputting programs and data, for debugging, for assembling large program systems from sub-sections and libraries, and so on.

Ferranti Pegasus II computer in use, c 1958. © Science Museum / SSPL

Ferranti Pegasus II computer in use, c 1958. © Science Museum / SSPL

Pegasus and the Science Museum
The Science Museum Pegasus, serial number 25, has been re-located at least eight times in its life, including a period in Sweden. The museum acquired it from UCL London in 1983 and it was initially displayed in Manchester where it was occasionally maintained by a colleague and myself. After a couple of years the machine moved back to London.

When the Computer Conservation Society was formed in 1989, a group of expert volunteers re-commissioned and demonstrated Pegasus at the museum. It was put on prominent display in the Computing gallery in 2000, where for the first time in its long life, Pegasus was on view to the public. It is a tribute to the quality of the original engineering that Pegasus survived this repeated stripping down, moving, and re-assembling.

For nearly a decade Pegasus was demonstrated every fortnight, but in 2009 a fault with the machine required it to be shut down and Health and Safety considerations subsequently stopped further operation. This historic, 60-year old computer continues to be an important artefact in the Science Museum’s Computing and Data Processing collections.

For more information on Pegasus, read “The Pegasus Story” by Simon Lavington published by the Science Museum. In 2015, the Computing gallery will close, reopening in late 2016 as the new Mathematics gallery. You can discover more about the history of information and communication technologies in the Information Age gallery, opened in October 2014.

Think, Build, Create! New Code Builder Workshops

Audience Engagement Manager Jen Kavanagh explains how the new Code Builder workshop aims to inspire the next generation of programmers

The Science Museum’s new Information Age  gallery explores communication and information technologies and processes, including the development and use of computer networks. Computing is currently a hot topic for schools, with the launch of the new computer science curriculum coinciding with the opening of this new gallery. As a result, the team here wanted to explore how we could effectively respond to this through the gallery’s learning programme.

Early computing objects on display in Information Age tell stories of user innovation, from Tim Berners-Lee’s NeXT Cube computer to the Pilot ACE used by Alan Turing.

Tim Berners-Lee's NeXT computer, which is on display in the Information Age gallery.

Tim Berners-Lee’s NeXT computer, which is on display in the Information Age gallery. Image credit Science Museum / SSPL

These amazing stories show the huge potential of computers, and our new tinkering workshop, Code Builder, aims to build on these further.

After an introduction, the group is set a task to use basic coding language to devise and input procedures into an online programme, test, rework them and see live results. These results come in the form of a small robot, Robotiky, which is programmed using bespoke online software.

A Robotiky robot created at a Science Museum Code Builder workshop

A Robotiky robot used in Science Museum Code Builder workshops

Coded instructions are written and simulated on screen, and then sent to the robot via a USB connection, allowing the students to see their code in action. The session encourages the development of logic and computational thinking skills, through trial and error, as well as exploring the interaction between hardware, robot, software and computer programme.

This workshop is designed to complement a number of areas of the computing curriculum at key stages 3 and 4. These include evaluating and applying information technology to solve problems, as well as helping pupils understand the hardware and software components that make up computer systems and how they communicate with one another and other systems.

Code Builder runs twice a day every Thursday during term time. Sessions last an hour and are free for schools to attend. To book visit our website.

How did tea and cake help start a computing revolution?

Today (17 November) marks the 63rd anniversary of the LEO 1 (Lyons Electronic Office 1) computer, the first computer to be used in the workplace. 

In 1950 if you fancied a cup of tea or a piece of cake you might have gone to a Lyons tea shop. J Lyons & Company ran tea shops across Britain. But the company was also interested in improving the way its work was managed and conducted, so it decided to build a computer that could support the collection and analysis of this information. Brought to life on 17 November 1951, LEO I played a crucial role in the development of a new computer age.


Working with the team at the University of Cambridge that had built the EDSAC computer in 1949, Lyons developed the LEO I, assembling it at the Lyons main factory building in West London. The computer ran its first program on 5 September 1951, valuing the cost of goods that came out of the bakeries.

Leo I electronic computer, c 1960s

Leo I electronic computer, c 1960s

The company LEO Computers Ltd was formed in 1954 and went on to build LEO II and LEO III. These were installed in many British offices including those of Ford, Customs and Excise, the Inland Revenue and the Post Office. The later models were exported as far as Australia and South Africa.

You can find out more about the LEO computer in our Information Age gallery, which looks at the last 200 years of how communications technology has transformed our lives.

A page from Babbage’s scribbling book with notes on his automaton for playing noughts and crosses or ‘tit tat to’, from a collection of over 20 notebooks held at the Science Museum Library & Archives in Wroughton.

The ingenious inventions of Mr Babbage!

By Cate Watson – Content Developer on the Babbage display

Although Charles Babbage is best known for his calculating engines, plans of which are now on display in the Computing gallery, he was a life long inventor with a passion for improvement.

As a 16 year old Babbage nearly drowned when he trialed his newly invented shoes for walking on water. This setback failed to discourage him and Babbage’s inventions ranged from designs for a locomotive ‘cow catcher’, an automaton for playing noughts and crosses, a ‘black box’ recorder for monitoring railway tracks and ‘speaking-tubes’ linking London and Liverpool among many other ideas.

Cartoon based on Babbage’s design for a ‘cow-catcher’.

Cartoon based on Babbage’s design for a ‘cow-catcher’. Image credit: Science Museum / Science & Society Picture Library

Babbage fervently believed that new inventions should be freely available to all – when he constructed the first known opthalmoscope in 1847 for internal eye examinations he refused to patent it. The credit went to Herman von Helmhotz 4 years later instead.

You can see another of Babbage’s inventions in the Museum – an occulting light mechanism to help with ship navigation. Ship captains used lights on shore to steer by but the increasing number of lights on the coast led to confusion. Babbage designed a light with mechanical shutters to create a unique flashing signal for ships.

A page from Babbage’s scribbling book with notes on his automaton for playing noughts and crosses or ‘tit tat to’, from a collection of over 20 notebooks held at the Science Museum Library & Archives in Wroughton.

Frustratingly for Babbage, this invention, like many of his ideas, found no favour at home. It did however sufficiently impress the Russians, who used the principle of his signalling lights against the British in the Crimean war.

Babbage’s foresight wasn’t limited to his inventions. He predicted the end of the coal mines and recommended tidal power instead, commenting that if posterity failed to find a substitute source of power it deserved to be ‘frostbitten’!

See more of Babbage’s inventive drawings in a new display in the Science Museum’s Computing gallery.

Plan for Babbage's Analytical Engine

Iconic Babbage drawings to go on display

By Cate Watson, Content Developer on the Babbage gallery

Plans for a Victorian computer and a giant calculator are going on display in the Science Museum next week.

Charles Babbage (1792-1871), computer pioneer, inventor, reformer, mathematician, philosopher and political economist.

Charles Babbage, the Victorian mathematician and inventor spent much of his life designing calculating machines, first the Difference Engine, and then in later years, the Analytical Engine that bear so much resemblance to modern computers. Unfortunately, Babbage never got to see any of his machines built. After quarrelling with the government his funding dried up and he couldn’t afford the costs of construction. All Babbage could do was endlessly refine his plans for the engines.

Apart from a few test models, which are on display in the Science Museum, technical plans are all Babbage left of his inventions.  The Museum – which holds the Babbage archive, the most complete collection of Babbage’s technical drawings and notebooks in the world - used these plans to build Difference Engine no. 2 in 1991, proving that the engine would have worked. Visitors will now be able to compare Babbage’s own drawings to the modern model of the Difference Engine in the Computing gallery.

The plans of the Analytical Engines show the many similarities between it and our electrical computers although it was designed over 170 years ago. The engine has a memory, a central processor, an input device in the form of punched cards that could program the engine and a printer. Instead of modern day circuit boards and silicon chips, a combination of cams, clutches, cranks and gears would have worked out calculations.

The most iconic plans of the Difference and Analytical Engines will be on display in the Computing Gallery from Thursday 24th January. This is the first time these drawings have been on show, complete with an annotated breakdown of how the engines would have worked.