I just remeber thay days of the ZX spectrum. The whole system was pre-built, and the OS was built in too.
If a program was written it either worked or it didn't. There was no chance of a program working with this card, but not that, as there was just the spectrum (that it had been written for), and that was it.
It was simplistic, but it did not jerk me about. the bits worked, or not. If not, you took them back, and they did not work on the computer in the shop, as the one in the shop was compleatly the same as mine.