Sinclair ZX80 Home Computer from the eighties


SINCLAIR ZX80 HOME COMPUTER

by Mark Nobes, chief editor

The ZX80 started a new revolution in home computing, and its release on January 29th 1980 was perfectly timed at the start of an exciting new decade.

In 1980, the ZX80 was the smallest and cheapest home computer on the planet - you could balance one on the palm of your hand! It sold for £99.95 (or £79.95 in kit form), and was well-received in both the UK and US. Okay, it was prone to overheating, and the membrane keyboard was rather annoying, but the inclusion of such a keyboard helped Clive Sinclair (now a Sir, of course) to keep his costs down.

Selling at such a low price did have its drawbacks, and the machine had many limitations. There was no colour or sound, very limited memory, and no video chips - graphics functions were left to the CPU, which meant it was very slow and prone to flickering.

The ZX80 featured a whopping 1kB of RAM and 4kB of ROM (which held the BASIC programming language). Sinclair sold around 50,000 units in all. Unlike the mass-marketed ZX81 and ZX Spectrum, it is now a collector's item as there are very few surviving units that still work.

The ROM contained the operating system and Sinclair BASIC. Unlike the BASIC language found on many other computers of the time, you did not type in the commands, but instead selected them using the keys on the keyboard. 

DISPLAY

To use the ZX80, the user needed to connect it to a TV set using the RF connector. The display was in black and white only, but this actually gave the machine an advantage as it was compatible outside of the UK, as PAL, SECAM and NTSC were not required for monochrome displays.
Because the computer used a combination of hardware and software to create a vidoe signal, a picture could only be displayed while it was idle and not running a program. The display would go blank temporarily when the processor was busy, such as when a key was pressed or a program was running.
The display was character based and crude graphics could be displayed using simple block characters. Games for the machine used a combination of block graphic characters (often for mazes and platforms etc.) and standard keyboard characters. 
ZX Kong Game by Paul Farrow
As you can see from this impressive Donkey Kong game (copyright  2010 Lightning software) which has been programmed using machine code, "H" characters were used to create ladders.

Storage

The ZX80 also included a built-in cassette port allowing the use to save BASIC programs to cassette. 

PAC-MAN ON THE ZX80

This video features a recently programmed, flicker-free version of Pacman for the ZX80 which is available to buy, believe it or not! Of course, it looks flickery in the video because of the old CRT TV screen which is being used to demonstrate the game. But this gives you an idea of what can be done which such limited hardware, at least.

ZX80 on the cover of Personal Computer World April 1980
Personal Computer World April 1980

SPACE INVADERS on a ZX80

Here is a ZX80 running a flicker-free game of Space Invaders at a vintage computer show. Actually, I'm more interested in that funky, space age monitor!