Since their conception at the start of the 20th century, few technologies have progressed as much as the computer. The development of first the valve, then the transistor and finally silicon chips have lead to the processing power of computers approximately following Moore’s Law which states that the number of transistors that can be inexpensively placed on a chip will approximately double every 2 years.

In the 1980s computers were starting to become affordable for the average home user and among the most popular were the Sinclair range. The ZX81 was the first home computer of many people who are now around 25 years old and older.

Sinclair ZX81

The ZX81 was the big brother of the older ZX80 and was released in 1981 (that’s 28 years ago, if you want to feel old ). It had a Zilog Z80 processor, like the later Amstrad CPC range, and a wopping 1KB of RAM (try to get your Vista in THAT Microsoft!).

The screen was 32 x 24 characters which lead to some rather blocky graphics, but no one seemed to mind. Several games were released including a version of chess that fit in the 1KB of RAM.

The original price was £49.95 – but that came unassembled: you had to solder the unit together yourself. If you wanted the hard work done for you the price rose to £69.95.

Interestingly the ZX81 didn’t use the ASCII character set but instead used its own proprietary character encoding where 0 was space, 1 – 10 were block graphics and the letters and numbers were represented by other codes.

The ZX81 was eventually replaced by the ZX Spectrum which was capable of much better graphics, including colour, had at least 16KB of RAM and for which hundreds of games were released.