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SBCA MEM ;A-MEM-C
SBCB MEM ;B-MEM-C
If the carry flag is set, one is subtracted from the result of the addition.
The borrow uses the carry flag bit. The carry flag may be set or cleared by a previous subtraction.
Using the “add with carry” instructions allows multibyte additions of any byte length.
When subtracting, a borrow occurs whenever a larger number is subtracted from a smaller number. The carry flag is used to indicate a borrow after a subtraction. When set, the carry flag indicates that a borrow has occurred.
The following subtraction results in a borrow.