Gallery: The evolution of the PC

Sinclair ZX81

British company Sinclair Research introduced low cost personal computing to the world with the ZX series of machines.

The Sinclair ZX81 cost just £69 ($100 in the U.S.) on release in 1981 and was a follow-up to the Sinclair ZX80, which is now extremely rare.

With a 3.25MHz processor and 1KB of memory the ZX81 had a membrane keyboard, could connect to an TV and load programs from an ordinary tape recorder.

Photo credit: Nick Heath/silicon.com