The X 86 Microprocessors: Architecture, Programming and Interfacing (8086 to Pentium) 2nd Edition by Pearson

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THE

x86 MICROPROCESSORS

3.5 | Logical Instructions

Table 3.7 gives the complete list of logical instructions and the function performed.

Example 3.23

Find the result and the state of the flags CF, ZF and OF due to the following instructions.

Given AX = 008CH, BX = 345EH, CX = 67EBH

i) AND BL, CL

ii) OR AH, BH

iii) XOR AL, CH

iv) TEST AH, BL

Solution

i) AND BL, AL

BL = 5EH 0101 1110

CL = EBH 1110 1011

4AH 0100 1010

After this operation, BL contains 4AH. CF = 0, OF = 0, ZF = 0.

ii) OR AH, BH

AH = 00 0000 0000

BH = 34H 0011 0100

34H 0011 0100

After this operation, AH = 34H. CF = 0, OF = 0, ZF = 0.

iii) XOR AL, CH

AL = 8CH 1000 1100 ...