Sinclair ZX81

Launched on5 March 1981, Sir Clive Sinclair’s second home computer (following the ZX80) was a massive success, selling hundreds of thousands across the UK. Available from Sinclair Research Limited, it could be purchased assembled for £69.95 or as a kit for only £49.95.

Manufactured by Timex Corporation in Dundee, it came with a BASIC interpreter, Z80 processor and a whopping 1k of base memory. The memory could be upgraded to 16k with an add-on module – Unfortunately not the most stable of accessories. The slightest vibration or movement would break the fragile link and cause the computer to reset itself.

The solid lump of black plastic was nicknamed “the doorstop” by some, and it didn’t really have a keyboard as we know them today – you had to type on a membrane/bubblewrap hybrid – and its graphics were blocky and black and white.

Despite the reliability issues (when WH Smith began selling the unit the company had to order a third more than it required so it had sufficient replacements) the ZX81 was extremely successful and nurtured a body of enthusiasts, many of whom went on to important roles in the British computer industry.

Clive Sinclair became a millionaire, received a knighthood and was awarded an honorary doctorate of science by the University of Bath in 1983.

Sinclair was the first to develop and market home computers in Britain. In June 1978 he launched the MK14, a microcomputer kit. Then, Sinclair’s chief engineer Jim Westwood developed the ZX80 which was sold in ready-made form as well as in a kit. At the time it was the smallest and cheapest in the world, retailing at £99.95.

It was followed by the ZX81 and in April 1982, the ZX Spectrum appeared with a colour display designed to be used with contemporary televisions.