H in the above program means "hex", don't treat those values as octal!
Back in the old days there were magazines and journals for programming help. Programming a computer was just the way you did things. There was basic, but in the earliest days no one even had that!
So in order to survive you just had to learn it by whatever way possible.
The most exciting thing about the kits that I build is the idea that I'm helping preserve some of the knowledge and allowing people to experience these things!