That manual is great! I highly recommend reading through it for anyone interested in computing history - and anyone interested in how to communicate clearly in technical writing.
Here's a fun report from someone who had the 205 as their first personal computer:
> One of the programs that I wrote during the summer at the University of Utah involved a loop that was exactly 20 instructions long. That meant the entire loop could be loaded into the high speed memory. It didn't even need the jump instruction from the end of the loop back to the beginning. It would just continue execution from the duplicate of the code in the next block on the drum. The trouble was there was no way to exit the loop.
> I needed a "Skip on Minus" instruction. There was a "Skip on Plus", but no "Skip on Minus". The EE grad student who maintained the machine was a guy named Joe. I wish I could remember his last name. Anyway, I told him I needed a "Skip on Minus" instruction. He said, "I'll put one in". He disappeared behind the cabinets with circuit diagrams and a soldering iron. He called out, "the op code will be 51".
> I wrote my program with a "51" instruction. It worked perfectly. And so the University of Utah had the only Burroughs 205 Datatron in the world with a "Skip on Minus" instruction.
Algorithms (implemented in parallel with electronics):
Secondary storage algorithms:
Read(addr): While address != addr: nop Return read_head_value
Write(addr, data): While address != addr: nop Write data
Fast storage:
Read(addr): While address % 10 != addr: nop Return read_head_data
Write(addr, data): While address % 10 != addr: Write read_head_data Write data