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Unformatted text preview: Class notes for the week of November 19th Addition: Adding two decimal numbers is easy: 586 +267 853 We add starting with the rightmost column. In this case we add 6 and 7 to get 13. We don't write the 13 down on the bottom row though, instead we write the 3 down and carry the 1 to the next column. If we show all the carries we get 11 586 +267 853 There is never a carry into the first column. In this first column we only add two digits, one from each of the two numbers. In the subsequent columns we may need to add three digits one from each of the two numbers, and another from the carry digit. Binary adders: The situation is similar when adding binary numbers; there are only two digits in the rightmost column since there is never a carry digit for this column. The other columns may have three digits since there could be a carry digit for these columns. Circuits can be built to implement these addition functions. A circuit that adds two bits is called a half adder and is suitable for use when adding the leftmost column. A full adder adds two bits, but has an additional input for the carry in from a previous column. Both circuits have two outputs, a sum bit and a carry-out bit that will be used by the next column to the left.
A Sum B A Sum B C a rry o u t C a r r y in Half Adder Full Adder
C a rry o u t Details of these adders are presented in prelab 10 (half adder) and lab 10 (full adder). ...
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This note was uploaded on 09/26/2008 for the course ESE 123 taught by Professor Westerfield during the Fall '07 term at SUNY Stony Brook.
- Fall '07