Sinclair Research

Happy Birthday, Sinclair ZX81 Computer!

Despite its limitations, the ZX81 was a revolution, because it cost just £49.95 in the U.K.—massively cheaper than anything else on the market. It was also available in normal retail stores, rather than specialty computer shops.

It really was the people’s computer, and for many it was their introduction to home computing and computer programming. Incidentally, at that cheap price, it was a kit you assembled at home (a soldering iron was required). You’d have to pay an extra £20 if you wanted a pre-assembled unit. In the U.S., the fully-assembled unit cost $149.95.

The ZX81 was also expandable. You could upgrade it from its RAM using an…