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Table Of Contents
Modern Computer Architecture and Organization - Third Edition
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General-purpose processors support the addition operation for data calculations and for managing the instruction pointer. After executing each instruction, the processor increments the instruction pointer to the next instruction. When a processor supports multi-word instructions, the updated instruction pointer must be set to its current value plus the number of words in the just-completed instruction.
An adder circuit adds 2 data bits and an incoming carry, producing a 1-bit sum and a carry output. This circuit, shown in Figure 2.15, is known as a full adder because it includes the incoming carry in the calculation. A half adder adds only the two data bits without an incoming carry.

Figure 2.15: Full adder circuit
The full adder uses logic gates to produce its output as follows. The sum bit S is 1 only if the total number of bits with a value of 1 in the collection A, B, Cin is odd. Otherwise, S is 0. The two XOR gates perform this logical operation. Cout is 1 if both A and B...