The Sinclair ZX81 was my first home computer - my brother had one as a Christmas present in 1981, and I bought it off him the next year, so that he could upgrade to a ZX Spectrum.
With just 1K of built in RAM, and a 16K RAM pack expansion, I was set to go. I was soon typing in listings from the computer magazines and teaching myself both ZX BASIC and Z80 Machine Code along the way ( I couldn't afford an assembler and editor, so it was all worked out by hand from the comfort of my small bedroom). With no colour or sound, and just 64x48 pixel resolution, it was the cutting edge at the time. Advertisements said it was powerful enough to run a nuclear power station!
I upgraded the machine over the years, trying out add-on sound, 64K and high resolution (256x192) graphics interfaces, but the number of software titles which supported these could be counted on one hand. I put it into a full sized keyboard, and loved playing the pseudo hi-res games by Software Farm (Forty-Niner and Rocket Man) which did not need any new hardware; but when the Sinclair QL was launched in 1984, I bought myself one of those and moved onto the world of 68000 machine code, with 4 or 8 colours in up to 512x256 pixels and even a basic beep command - pure luxury!
My business (RWAP Software) was then launched in 1986 to review QL software, and along the way offer bug-testing and fixing for third party titles, mainly to make them useable on systems with floppy disks; as well as ensuring some games could actually be completed!
The ZX81 then seemed to fall into dis-favour - as the internet bloomed, most of the discussion was around the much more popular ZX Spectrum and it was rare to find any discussion about the ZX81. I assumed that many had rusted (like my original one when brought down from the attic). However, in 2008, I was asked about producing replacement keyboard membranes for the ZX81 (by this time, I was already selling a steady stream of Spectrum membranes and some QL membranes), so I decided to launch the ZX81 Forums in order to try and guage interest, and then eventually took a plunge, ordering 250 replacement membranes, expecting to sell about 100 over a period of years.
The ZX81 forums proved a call to arms, and more and more people were digging out their ZX81s and buying replacement membranes (I have now sold over 1000 membranes). It seemed there was still a lot of love for this little machine - particularly as it was easy to use to learn about electronics (with a simple 8 bit bus) and start designing new hardware. Out of this, I came across SirMorris who had decided to try and design a new SD card interface (complete with 32K) for instant loading and saving of games to the ZX81 and persuaded hiim that there may well be a market for his interface rather than keeping it just for himself and maybe a handful of others. We talked about the design and potential to add a joystick interface and maybe an AY sound interface and the ZXpand was launched in June 2010
Access to a fast, reliable source of saving and loading re-invigorated the ZX81 community even further, with new games (including many with hi-resolution graphics) being developed over the past 5 - 6 years, and with the ZXpand's ability to work with the Sinclair ZX80, there have even been some new game releases for that humble computer.
As to whether the ZX81 was ever used to power a nuclear power station? Well probably not, although some years ago, I did acquire a ZX80 which had been used for many years in a power station to calculate certain flow readings, so who knows.. Maybe the stories that the USSR bought up a stockpile of ZX81s to use as a low cost computer for their ICBMs was not as far-fetched as might first appear.
