<nostalgia>
I remember PL/M: way back in my very first "real" job after graduating, we were using PL/M86 to rogramme the latest, cutting-edge 8086 processors on Intel MDS800 systems, complete with 8" floppy drives. Halcyon days!
</nostalgia>

Unfortunately, I have no manuals now.

"PS I know I should be using assembly"
Why?
There is no reason to assume that Assembler is inherently "good," whilst higher-level languages are inherently "bad"
You need to ensure that you are using an appropriate language for your particular circumstances.
See other recent threads!!