You could buy a ZX81 in high-street shops like WHSmith. It was extensively used in schools and colleges for educational purposes. Many people working in the tech industry had their first computer experiences with the ZX81.

Launched on 5th March 1981 by Clive Sinclair as the successor to the ZX80, it was available ready-built (£69.95) or in kit form (£49.95). Its low cost and relative power made it extremely popular. It was also well supported with software and peripherals by both Sinclair and other companies. 

Sinclair's advertising claimed that its good design created a higher specification at a lower price. The number of chips was reduced from 21 in the ZX80 to 4 in the ZX81. It was a small machine, weighing 350 grams in total. Designed by Rick Dickinson the in-house industrial designer at Sinclair Research Ltd, the ZX81 won a British Design award.

With only 1K of RAM and 8K of ROM, the ZX81 was not capable of colour graphics. However, this did not stop sales with over 1.5 million units sold.

The ZX81's successor, the ZX Spectrum, was released in April 1982. The ZX81 was discontinued in 1984.