07-14-2003, 05:22 AM
1) the method where if the digit you're subtracting is greater than the one above, you borrow 1 from the top of the next digit position and add 10 to your top digit.
2) the method where if the digit your subtracting is greater than the one above, you add 1 to the bottom of the next digit position, and add 10 to your top digit.
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AGAMEMNUS,
Try subtracting 123 from 9999. If this works, try subtracting 999 from 10000. If this in turn doesn't work, then the subtract routine is using method #1 above. Implementing method #1 is not easy, actually it's a mess.
Most Americans who have to implement subtraction will use method #1 because that's what they were taught in school, sad to say. My mother was from Europe, and before I went to school she taught me the method #2 of subtracting. So, when I first implemented a subtract routine, it was easy.
*****
2) the method where if the digit your subtracting is greater than the one above, you add 1 to the bottom of the next digit position, and add 10 to your top digit.
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AGAMEMNUS,
Try subtracting 123 from 9999. If this works, try subtracting 999 from 10000. If this in turn doesn't work, then the subtract routine is using method #1 above. Implementing method #1 is not easy, actually it's a mess.
Most Americans who have to implement subtraction will use method #1 because that's what they were taught in school, sad to say. My mother was from Europe, and before I went to school she taught me the method #2 of subtracting. So, when I first implemented a subtract routine, it was easy.
*****