Timex Sinclair 1000; https://en.wikipedia.org/wiki/Timex_Sinclair_1000
I was in the 8th grade, I think. Z80 processor, 2k RAM, membrane keyboard. I loved programming on it, because it was a totally new experience. I wanted the 16k expansion so badly. I had to use a personal cassette tape recorder to save/load software; I recall having to find the right volume level, and using white-out to mark the volume knob.
I not only learned programming, but diagnostics. I still have fond memories of that $99 computer.
Related, OOP for Out Of Pocket. In software, its Object Oriented Programming. My programming lead uses the first meaning in email frequently