CompuServe Messages

Resident library routines are always allowed to trash the A0/A1 and D0/D1 registers. These are typically called 'temporary registers', and are used for scratch purposes. The reason for scratch registers is to make it so that routines are constantly pushing and popping registers, which can slow things down alot. So, if you need to keep A0/A1/D0/D1 preserved over calls to resident library stuff (or indeed, really if you're doing any kind of call), then you should push 'em before the call and pop 'em after. Oh, the exception to this rule of course is that some routines return values in D0 😎 -Mike