Integer overflow: Difference between revisions

=={{header|Z80 Assembly}}==

===Zilog Z80===

The <code>P</code> flag represents overflow after an arithmetic operation, and bit parity after a bitwise or logical operation. Arithmetic operations will result in overflow if the 7F-80 boundary is crossed. One quirk of the Z80 instruction set is that program counter relative jumps cannot be done based on overflow; only calls, returns, and jumps to fixed memory locations.

<lang z80>

ld a,&7F

add 1

jp pe,ErrorHandler ;pe = parity even, but in this case it represents overflow set</lang>

===Game Boy===

The Game Boy is missing all control flow commands pertaining to the overflow flag. However, overflow can still be detected in theory, but it's a difficult process that requires the exclusive or of the carry flag and whether a subtraction changed the sign of the accumulator or not. Since the Game Boy's CPU cannot natively detect overflow, the CPU <b> will continue with a wrong result.</b>