!lm10
!rm76
Two Ways to Compare a Byte.........................Lee Meador

I have noticed two ways to compare a byte used inside DOS and other Apple software.  In the cases I am thinking of, the following code required the Y-register to be zero.  The first way I have seen is straightforward:
!lm15
LDA ...       BYTE TO BE TESTED
CMP #$19      VALUE WE WANT TO TEST FOR
BNE .1        ALSO AFFECTS CARRY STATUS
LDY #0        IF =, CARRY SET
...
!lm10

The other way is a little trickier, but it saves one byte:
!lm15

LDA ...       BYTE TO BE TESTED
EOR #$19      VALUE WE WANT TO TEST FOR
BNE .1        DOESN'T AFFECT CARRY STATUS
TAY           A AND Y BOTH ZERO
...
!lm10

This may help you understand some of those disassemblies you are making, or help you save a byte here and there.
