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Solved Problem - Binary Subtraction

Question

Perform the following sums using binary numbers:

First we choose to use 8-bit true magnitude format. In this format:

+75 = 01001011 ; +42 = 00101010

1.	01001011	+75 in true magnitude format
	+11010110	2's complement of +42
	________
	00100001	this is +33 in true magnitude format

2.	10110101	2's complement of +75
	+11010110	2's complement of +42
	________
	10001011	sign bit is 1 so perform 2's complement
	01110101	2's complement of last line
	11110101	replace sign bit
	________
	11110101	-117 in true magnitude format

3.	-75-(-42) = -75+42 = 42-75 and so
	00101010	+42 in true magnitude format
	+10110101	2's complement of +75
	________
	11011111	sign bit is 1 so perform 2's complement
	00100001	2's complement of last line
	10100001	replace sign bit
	________
	10100001	-33 in true magnitude format