Sinclair ZX81
Computing for under £70
Clive Sinclair's black wedge computer brought programming to Britain's bedrooms, despite its 1KB RAM and membrane keyboard.
Overview
The ZX81 arrived in 1981 and did something remarkable: it made computing affordable. At £69.95 (kit form) or £99.95 (assembled), it cost less than a television. Over 1.5 million sold, introducing a generation to programming through its built-in BASIC interpreter. The limitations were severe, but the possibilities felt infinite.
Fast facts
- Launch: March 1981.
- Price: £69.95 (kit), £99.95 (assembled).
- CPU: Zilog Z80A at 3.25 MHz.
- RAM: 1KB (expandable to 16KB).
- Display: 32×24 characters, black and white only.
- Input: 40-key membrane keyboard.
- Storage: cassette tape.
- Designer: Rick Dickinson (industrial design).
- Sales: over 1.5 million units worldwide.
The limitations
The ZX81 taught constraint:
1KB RAM
- ~900 bytes after system variables
- Programs measured in lines, not pages
- Variables consumed precious memory
- PEEK and POKE optimised every byte
Membrane keyboard
- Flat, unresponsive keys
- Multiple key presses required for keywords
- “Dead flesh” feel became infamous
- Third-party keyboards were popular upgrades
No sound
- Complete silence unless you counted tape loading
- Some programs used RF interference tricks
Display glitches
- Screen went blank during computation (FAST mode)
- SLOW mode showed display but ran… slowly
The design
Rick Dickinson’s black wedge design was distinctive:
- Sloping profile hid circuit board economy
- Black plastic looked modern, not cheap
- Compact footprint suited bedroom desks
- Became template for Sinclair aesthetic
The 16K RAM pack
The wobble that crashed a thousand programs:
- Plugged into back expansion port
- Notorious for loose connection
- Slight movement caused system reset
- Users developed techniques to stabilise (Blu-Tack, rubber bands)
Software ecosystem
Despite limitations, software flourished:
- Type-in listings: Sinclair User, books, magazines
- Commercial games: 1K Chess became legendary
- Business applications: word processors, databases (with RAM pack)
- Educational: schools adopted the ZX81 in large numbers
Path to the Spectrum
The ZX81 created demand for more:
- Users wanted colour, sound, better keyboard
- Clive Sinclair delivered the ZX Spectrum in 1982
- ZX81 owners knew computing was worth pursuing
- Many simply moved up to the Spectrum and kept going
Legacy
The ZX81 launched more programming careers per pound than any machine before or since. Its limitations taught efficiency and creativity. The 1KB games remain marvels of compression. And the wobbling RAM pack taught generations that computers were physical objects, not magic boxes.