The BBC and Master Computer Public Domain Library

Integer Positive Routine

Submitted by Steve Fewell

Routine: ipos
Name: Integer Positive
Starting Address: &ACBE
Entry criteria: The IWA contains the integer to make positive.
Exit: If the IWA contained a negative value, it will now be positive, otherwise IWA will be unchanged.

Description:
Check the most significant byte of the Integer Number in the IWA. If bit 7 of this byte is set [N flag], the IWA contains a negative number, so the icomp routine is jumped to (to compliment the value). Otherwise the routine exists with A = #&40, indicating that an Integer number is being processed. [Note: The code for this is located in the icomp routine].

Disassembly for the integer positive routine