Computer Museum - Sinclair ZX81  
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My two ZX81s, serial number 003-007213 (on the left) and serial number unknown.
Introduced in 1981, the ZX81 was an improvement on the ZX80 but also came with only 1KB of on-board memory.
The keyboard, still flat but with easier to read keys, had been re-arranged to allow for additional BASIC keywords. The flat keys made programming tedious but some enterprising manufacturers produced keyboards which had raised keys that fitted over the top.
The memory was still only 1KB but an additional 16KB could easily be added at the rear. These RAM cartridges. like the one on the left, had a reputation for wobbling, causing the computer to crash. But third-party versions like the Cheetah and Memopak ones to the right soon appeared, designed to eradicate this problem.
A joystick could be used with an adaptor. The one on the left is a Sinclair model, while the one on the right is a Kempston.
In the UK, the ZX81 was many people's first experience of computers. A wide range of software was produced including games and utilities. The computer also introduced the possibility of learning to write your own programs.
My second ZX81 has been modified to work with modern TVs via the AV connection.
ZX81 Programming        
(Steven Vickers /        
Sinclair Research)        
1K ZX Chess. (Artic Computing).
Cassette 50. (Cascade).
Club Records. (16K). W H Smith (ICL).
Collector's Pack. (16K). (ICL, 1982).
Telephone, Note Pad, Bank Account. (16K). (Sinclair Research, 1981).
VU-CALC. (16K). (Psion, 1982).
Super Programs 5. (16K). (ICL). Martian Knock Out, Graffiti, Find the Mate, Labyrinth, Drop a Brick, Continental.
Super Programs 6. (16K). (ICL). Galactic Invasion, Journey into Danger, Create, Nine Hole Golf, Solitaire, Daylight Robbery.
Super Programs 7. (1K). (ICL). Racetrack, Chase, NIM, Tower of Hanoi, Docking the Spaceship, Golf.
These three tapes are very sensitive to volume level. Side 2 Tape 6 not successfully loaded.
Boxes for ZX81 (003-007213), Cheetah 16K RAM pack, Memopak switched 16K RAM pack and two Sinclai 16K RAM packs.
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