Ah yeah, I learned BASIC on one of those. My first programming experience. I also found that typing “SYS <random number>” (Commodore BASIC for “begin executing the machine language instructions at memory address <random number>”) would most likely drop you into some kind of cryptic under-world where strange symbols and letter-number things were everywhere (later on the teacher said “oh, that’s the machine language!” and then later on I learned that’s just the Commodore disassembler [aka monitor] which gets invoked whenever the CPU runs across a BRK or equivalent instruction).
I didn’t really absorb much about POKE and PEEK until I got my own Commodore 64 a year or two later. The PET’s display chip was very limited in what it could do, and most of the other memory mapped IO registers were the usual boring IO controller stuff (disk and tape) – stuff that was handled much more efficiently by LOAD and SAVE etc. (machine language in the BASIC and Kernel ROMs).
Had I know about that particular register I might’ve had a field day with it.
