Gotchas: Difference between revisions

SBC #4 ;eight minus four</syntaxhighlight>

 

The 6502 (and even its revisions) have ''no way to add or subtract without involving the carry flag.'' The "carry" is essentially the same as "carrying the one" that we all learned in elementary school arithmetic. <code>ADC</code> adds an extra 1 if the carry flag was set when the <code>ADC</code> was executed. <code>SBC</code> subtracts an extra 1 if the carry was ''clear'' when the <code>SBC</code> was executed (as stated before, on most other CPUs the equivalent of <code>SBC</code> behaves the opposite to the 6502).