I had that exact BIOS Interface Technical Reference manual, which (along with one describing the FAT, I think) were the only technical books that came with my P

I had that exact BIOS Interface Technical Reference manual, which (along with one describing the FAT, I think) were the only technical books that came with my PCjr. I spent the 10 hour drive home after purchasing it reading them, assuming that was the stuff I needed to know. I subsequently had a quite granular mental map of how higher-level software interacts with the hardware through BIOS and DOS interrupts, and knew a lot more than I generally needed to about where the MBR is stored, disk cluster size, etc. It was difficult times to learn about computers - no friends used them, there was no internet, so any knowledge acquired was hard-earned, and tended to really stick.