Sinclair ZX81

Sir Clive Sinclair's second home computer (following the ZX80) was a massive success, selling hundreds of thousands across the UK, although it didn't really have a keyboard as we know them - you had to type on a membrane/bubblewrap hybrid - and its graphics were blocky and black and white .

The solid lump of black plastic was nicknamed "the doorstop" by some, although it came with 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.