About the ZX81.mp3

By Mark Nobes

The ZX81 was the first cheap, mass-marketed home computer, selling a total of 1.5 million units before it was discontinued in 1984. It was truly innovative, and allowed the general public to get their hands on something that was once only available to businesses and hobbyists with huge amounts of cash to spare.

However, those who rushed out to buy a ZX80 will probably have been regretting the move after the release of the ZX81 (labelled the Timex Sinclair 1000 and 1500 in the U.S.). For a start it was half the price (£49.95 or £69.95 in kit form), it used just five chips (the ZX80 used 21) and it had a much better BASIC programming language. 

Sinclair ZX81 - Timex Sinclair 1000

As with virtually all other home computers around at the time, programs were loaded and saved via an external cassette recorder, which was the most popular and cheapest method in the early 80s. However, anyone who experienced using this method will know that it wasn't always reliable!  Floppy Disk drives were available to purchase as extras with other, more expensive computers such as the Atari 800, Commodore Vic 20 and IBM PC.

Rather than a dedicated monitor, the video display was viewed on a UHF CRT TV set (which was pretty standard at the time for home computers) which you connected via an aerial lead. 

Although the ZX81 was, by far, the cheapest computer available at the time, it was also the least powerful. It had just 1kB of RAM, although this was expandable to 16kB. With a maximum resolution of just 64 x 44 characters and mono display, it couldn't match the higher resolutions of the IBM PC with its 640 x 200 res, 16 colour display and the Atari 800 with a 320 x 192 res, 256 colour display. However, you had to be pretty well off to buy one of those superior models, and the whole point of the ZX81 was to make computing affordable for everyone.

An IBM PC would set you back $1265, an Atari 800 was $899.95 and a Commodore Vic-20 was $260. So at $99.95, the ZX81 was truly affordable and allowed more people than ever to join the home computing revolution, and you have to admire it for that. Plus, unlike other models, you could pick one up from a your high street store, such and Boots or WHSmith.

Learning to program the ZX81 was a fun experience on the whole, although somewhat frustrating, too, given the machine's limitations. But this was a challenge that forced the user to code their machine in a tight style that used as little code as possible, saving the use of the precious memory.
It was, of course, very satisfying to see the result of your very first playable game that you had programmed entirely by yourself, even if it was very basic! 
The membrane QWERTY keyboard could become problematic over time and wasn't particularly ideal for large amounts of typing. Nonetheless, it was cheap to manufacture and also didn't suffer from dirt and dust getting in-between the keys - a quick wipe and the dust was gone!
Membrana ZX81


By Knurrikowski (Own work) [CC BY-SA 4.0], via Wikimedia Commons

This fantastic image features a ZX81 with its original packaging accessories and ZX81 BASIC manual 

Sinclair ZX81
The ZX81 motherboard, Issue One version.

The ZX81 motherboard, Issue One version (public domain image)

Sinclair ZX81 Setup PhotoManipped
Here we have a typical Sinclair ZX81 setup, including cassette recorder, black-and-white television set and manual. Image credit: Mike Cattell [CC BY 2.0], via Wikimedia Commons


The Mighty ZX-81
ZX81 Close-up by Mikey Walters (Flickr: The Mighty ZX-81) [CC BY-SA 2.0], via Wikimedia Commons


Sinclair ZX81 Kit Build - Box
ZX81 interface - side views

ZX81 interface - side views (public domain image)


ZX81-16K-RAM pack
By Truthanado (Photo taken by user Truthanado) [GFDL or CC BY-SA 3.0], via Wikimedia Commons

The Sinclair 16K RAM memory module was externally connected to the ZX81 and was notoriously wobbly.

Sinclair ZX Thermal Printer

Sinclair ZX Thermal Printer for the ZX81

Timex Sinclair 1000 home computer (ZX81 variant)

The Sinclair Timex 1000 was a ZX81 variant which was sold in the U.S. (Public domain image)

Vintage Timex Sinclair 1000 (TS1000) Personal Computer, A Modified Version of the Sinclair ZX81, Used A Form of BASIC As Its Primary Interface And Programming Language, Sold For $99.95, Circa 1982
ZX81 on Your Computer magazine (Oct 1981)

The ZX81 with cassettes on the front cover of Your Computer magazine in October 1981.


Scramble Game

This video clip originally showed scramble on a Timex Sinclair 1000 (the US version of the ZX81) which had music (not being produced by the computer as it had no sound chip) and had been added by the video uploader.

However, this video suddenly disappeared off Youtube, and I've now replaced it with an even better one above which features running commentary.

By the way, if you owned a ZX81 then you will know that you also had to purchase the 16Kb expansion pack to play games.

Sinclair ZX81 PCB Revision 3 Keyboard
Sinclair ZX81 PCB Revision 3 Keyboard by Binarysequence (Own work) [CC BY-SA 4.0], via Wikimedia Commons


Gunfighter Game

Here's a  ZX81 game called Gunfighter. Well, it's a step-up from Pong, at least! Again, 16Kb would have been needed to play such a sophisticated game.


Crazy Kong is a version of the classic Donkey Kong, although in a much more primitive form, of course, due to the machines limitations.