## ALP Programming Guide and Reference

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### Description

Run the AAS instruction only after a SUB instruction that leaves the byte result in the AL register. The lower nibbles of the operands of the SUB instruction must have been in the range of 0 through 9 (BCD digits). In this case, the AAS instruction adjusts the AL register so it contains the correct decimal digit result. If the subtraction produced a decimal carry, the AH register is decremented, and the CF and AF flags are set. If no decimal carry occurred, the CF and AF flags are cleared, and the AH register is unchanged. In either case, the AL register is left with its top nibble set to 0. To convert the AL result to an ASCII result, follow the AAS instruction with OR AL, 30H.