Obligatory "When I were a lad..."
When I were a lad (actually in my late 20s/early 30s) I worked on software for a prototype data logger for an ice sounding radar. We used an S100 bus single card computer with a Z80 processor. The development system (using Wordstar, asm and link!) was an Osborne 1. It has left me with an enduring impatience with bloated software (I know what you can do in 2k of EPROM!) and memories of keeping vast amounts of code in my head so I could debug stuff in an environment where reassembling, linking , blowing a new EPROM and then testing the result could take an hour or more!
I still have the Leventhal Z80 Assembly language Programming manual on my shelf!