My mom was a programmer back in the 1950s. First thing in the morning, she would run a memory test. If it failed, she would slide out the failing tray of memo

My mom was a programmer back in the 1950s. First thing in the morning, she would run a memory test. If it failed, she would slide out the failing tray of memory (100 words by 36 bits, and tubes), hand it off to a tech to fix, slide in a fresh tray, and proceed. She had one CPU she worked on where you could change its instruction set by moving some patch cords.