1981, a ZX81, 1K of RAM and the RAM pack wobble

Back in 1981 my dad came home with a ZX81. I was 13. It had 1K of memory. Not one gigabyte, not one megabyte, one kilobyte: about the size of this paragraph.

It plugged into the telly and you saved your programs to a cassette recorder, at roughly 250 bits a second, give or take, with a screech that made the dog leave the room. The keyboard was a flat membrane you pressed like a lift button. In FAST mode the screen went blank while it was thinking, so you'd sit there staring at grey static wondering if it had crashed. Usually it had.

The first upgrade every ZX81 owner bought was the 16K RAM pack. It plugged into the edge connector on the back, and it wobbled. Not a lot. Just enough. You'd be an hour into typing in a program from a magazine, line by line, every PRINT and GOTO, and you'd press a key a bit too hard, the RAM pack would rock, and the screen would go white. Gone. All of it. No save, because saving took four minutes and you were going to do that "at the end".

The fix, as every 13 year old in Britain discovered, was Blu Tack. A big wodge of it between the RAM pack and the case. My dad, who was an electrician, looked at this and sighed and said nothing, which was his highest form of disapproval.

I learned two things from that machine that I've used for forty years since.

Save early, save often. I still hit save every few minutes without thinking. My wife says I do it in conversations.

Secure your connectors. Every flaky fault I've chased as an engineer, nine times out of ten it's a connector. A loose jumper wire on a breadboard, a ribbon cable not quite seated, a crimp that looks fine and isn't. When something works "until I touch it", stop debugging the code and start wiggling the wires. The ZX81 taught me that before I knew what a fault-finding procedure was.

The Amiga 500 came along in 1987 and I never looked back, but the ZX81 is the one I think about.

What was your first, and what did it teach you?

Cheers, Pete