THE modern world is impossible to imagine without computers. They fit on desks, in the laps – even the palm of the hand. But the first modern computers, one of the earliest begin, Cambridge university’s EDSAC, were very different. 1

Four elements define a modern computer: a program (a set of instructions); a central processing unit (CPU); a system of input and output; and a memory. The memory stores the program, the input and the results of calculations. EDSAC (Electronic Delay Storage Automatic Calculator), built by a team led by Maurice Wilkes (b. 1913), was the first practical stored Program electronic computer. It ran its first Program on 6 th May, 1949, calculating a table Of squares and a list of prime numbers. Its input was via punched paper tape. The memory was a huge array of tubes filled with mercury (called a delay line). The CPU was a system of thermionic valves and output was via a teleprinter. 2 Cracking cods Tow employees of the women’s Royal Naval Service operating Colossus, a World war II programmable computer that deciphered coded German military messages

During the 1950s, computers became slightly smaller – but they were still ‘mainframes’, found only in large companies and universities. Hardware developed fast and by the end of the decade computers had monitors and keyboards, though of input an output until the 1970s. In 1956, IBM ( International Business Machines) introduced magnetic disk memory – the hard disk. The first were housed in cabinets 1.5 meters (5 feet) high, could story about 5 megabytes of data, and cost $500,000. 3

Home PCs are as mush as EDSAC. EDSAC could carry out million instructions per second. A PC with an Intel Pentium 4 processor can do up to 10,000 million. 4

The first all electronic computers used vacuum tubes, electronic components that control electricity flow through. They were at the heart of how the computers carried out arithmetic. In 1947, an alternative was invented: the transistor, made with semiconductors, such as silicon. It was smaller, faster and more reliable than vacuum tubes and needed less power, In the 1960s, American engineer Jack Kilby ( ) realized that more than one transistor cam be basis of the integrated circuit (or ‘silicon chip’). 5

Manufacturers in the early 1970 miniaturized the electronic components on their integrated circuits to fit the entire CPU on one chip. American company Intel made the first commercial ‘microprocessor – and rapidly to home computers. The first was the Xerox Alto (1973). It cased a ‘graphical user interface’ (GUI) graphic icons rather than just words on a Small computer This Elliot 803 computer (left) from 1963 is smaller than many of its forebears because it was an all transistor model. This was one of the most successful British computer of the 1960s Smaller computer The DECPDP-8 computer (right), the first minicomputer (1965), with the case opened. Input and output were effected via punched paper tape, the switches on the front, or a connected teletype printer. 6

In 1952, research student AS Douglas wrote a simple naught and crosses game, called OXO, which ran on EDSAC. It is probably the first computer or video game. The player entered their move using a telephone dial and the game grid was displayed on a tiny screen. 7

First meeting of United Nations.1946 Hungarian-British physicist Gabor ( ) develops the concept of holography (although lasers will not be invented until 1960) The first commercial microwave oven goes on sale (the first domestic models were sold in 1952) American test pilot Chuck Yeager (b. 1923) breaks the sound barrier (about 760 mph) The atomic clock is introduced.1948 Swiss engineer Georges de Mistrals ( ) invents Velcro

Monitor – and was controlled by a mouse. The MITS Altair 8800 followed in 1975 and was the springboard for Bill Gates to launch U.S. software giant Microsoft, which made him the world’s richest man. The popularity of personal computing rose dramatically during the 1980s. There were several popular models – including, in Britain, the Sinclair Spectrum and Acorn’s BBC Microcomputer. The machine that made the biggest impact was the IBM-PC (1981). This ran using an operating system written by Microsoft called MS-DOS (Microsoft Disk Operating System). An operating system is a program that manages the computer’s hardware and runs the ‘application’ software. 9

In 1985, Microsoft introduced a GUI-based system called Windows. Another American company, Apple, had introduced a GUI-based personal computer in These tow systems now much more sophisticated still dominate the PC market Nowadays many billions of computer vastly more powerful than EDSAC are in use worldwide. Aside from business and personal computers, small ‘embedded’ computers control a huge range of machines from airlines to digital cameras. 10

No mouse The IBM-PC, introduced in More than 200,000 of these machines were sold in the world first year. It had no mouse, because the monitor could only display letters – on graphics. 11