The Sinclair ZX81 may have been the reason computers took off in the UK. The low-cost computer, which attached to a TV set and audio tape recorder, booted straight into a BASIC interpreter, making it very easy to get started with programming.

Looking back, the machine was tiny: it used a 1MHz Z80, had a 20x14 character display, and 1Kb of memory (which included the screen). But someone still wrote a decent chess game in 1Kb...

Ah, memories...

If you detuned the television a little bit and put the ZX81 into FAST mode, you could use timing loops to create music. My first routine was copied out of one of the many ZX programming magazines of the time, and produced 8 notes. They went "doo doo doo...doo doo dee doo doo" (wish I knew something about music). I'll always remember the tune.

The Sinclair ZX81's memory was so tight that the whole screen memory could barely fit in it. It had to store it compressed, which made programming quite uneasy. Hopefully, as soon as you added the 16K extension, the screen would be stored uncompressed. Most people added an el cheapo hard keyboard on top of the otherwise unusable flat one.

One nice feature of the ZX81 was that, when programming in BASIC, it let you press one key to get an entire keyword. (E.g., `P' for PRINT and so on.) It had extremely clunky graphics capabilities (roughly equivalent on what you might get on an HP48) but you could write fairly neat games on it. My favorite was Bombs Away.

The ZX81 also had the honor of being one of the first "sure you can get it in a kit" computers. I got mine this way, and at the time, (I was 12) it was a devil to put together. but once you hooked the Z80 up to all the other transistors and so forth, there was hardly anything that could go wrong. Except the infamous "RAM Pack Wiggle", whereby the much coverted 16K Ram Pack, which plugged into the "expansion slot" in the back of the ZX81, would wiggle, and dump RAM mid way through a programming session. this really burned after hours of tapping on the silkscreen keyboard, forgetting to save, then being forced to load the program in via cassette tape, which was hit or miss at best. Also margeted under the name "Timex-Sinclair 1000".

When I was 11, I learnt BASIC programming on a ZX81 in one afternoon.
I then coded some games, including a Russian Roulette program.
After lots of fun in my school brand new computer room, the teacher told me never to get back as he considered computers were a serious thing.
Nope.
They are tools and the ZX81 is my all-time favorite.
An interesting aspect of the ZX81 was due to its limitations which forced its users to optimize their code as much as possible.
It was called "The Initiator" in France and most of the hackers I know have had one.
I still have mine packed somewhere.
It is fully functional and includes a thermic printer, a 16kb extension, a mechanical keyboard and tons of books and tapes.
I'll give it to my children so that they will have the best learning tool ever.