The answer is -22. As you can see from this example, when you are dealing with a negative answer, you
must find two complements. The extra-order 1 must be generated before the end-around-carry can be
performed. If there is no extra-order 1, the answer is a negative number.
d. Binary Complement. A digital computer that uses the binary number system will use the binary
complement system. In the binary system, the two methods are: 2's complement (no end-around-carry)
and 1's complement (end-around-carry). First consideration will be given to finding the 2's complement
of any binary number. The 2's complement is performed by changing each digit to is opposite and adding
1 to the least significant digit (LSD).
Finding the 2's complement of any binary number can be simplified even further by starting at the least
significant bit (binary digit) position and inspecting each bit position for a 1. The least significant 1 and
all 0s to its right are copied without change. All bits to the left of the least significant 1 are changed. Of
course, identical results are obtained with the two methods.
(1) Binary Complement Subtraction.
Binary complement subtraction is performed by
complementing the subtrahend and adding. The method of 2's complement for subtraction is illustrated
below.
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IT0339
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