Logical Instructions 

AND : Logical AND 

This instruction bit by bit ANDs the source operand that may be an immediate register or a memory location to the destination operand that may a register or a memory location. The result is stored in the destination operand. 

Eg. AND AX, 0008H 

AND AX, BX 

OR : Logical OR 

This instruction bit by bit ORs the source operand that may be an immediate , register or a memory location to the destination operand that may a register or a memory location. The result is stored in the destination operand.

Eg. OR AX, 0008H 

OR AX, BX 

NOT : Logical Invert 

This instruction complements the contents of an operand register or a memory location, bit by bit. 

Eg. NOT AX 

NOT [5000H] 

XOR : Logical Exclusive OR 

This instruction bit by bit XORs the source operand that may be an immediate , register or a memory location to the destination operand that may a register or a memory location. The result is stored in the destination operand. 

Eg. XOR AX, 0098H 

XOR AX, BX 

TEST : Logical Compare Instruction 

The TEST instruction performs a bit by bit logical AND operation on the two operands. The result of this ANDing operation is not available for further use, but flags are affected. 

Eg. TEST AX, BX 

TEST [0500], 06H 

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SAL/SHL : SAL / SHL destination, count. 

SAL and SHL are two mnemonics for the same instruction. This instruction shifts each bit in the specified destination to the left and 0 is stored at LSB position. The MSB is shifted into the carry flag. The destination can be a byte or a word. 

It can be in a register or in a memory location. The number of shifts is indicated by count. 

Eg. SAL CX, 1 

SAL AX, CL 

SHR : SHR destination, count 

This instruction shifts each bit in the specified destination to the right and 0 is stored at MSB position. The LSB is shifted into the carry flag. The destination can be a byte or a word. It can be a register or in a memory location. The number of shifts is indicated by count. 

Eg. SHR CX, 1 

MOV CL, 05H 

SHR AX, CL 

SAR : SAR destination, count 

This instruction shifts each bit in the specified destination some number of bit positions to the right. As a bit is shifted out of the MSB position, a copy of the old MSB is put in the MSB position. The LSB will be shifted into CF. 

Eg. SAR BL, 1 

MOV CL, 04H 

SAR DX, CL 

ROL Instruction : ROL destination, count 

This instruction rotates all bits in a specified byte or word to the left some number of bit positions. MSB is placed as a new LSB and a new CF. 

Eg. ROL CX, 1 

MOV CL, 03H 

ROL BL, CL 

ROR Instruction : ROR destination, count

This instruction rotates all bits in a specified byte or word to the right some number of bit positions. LSB is placed as a new MSB and a new CF. 

Eg. ROR CX, 1 

MOV CL, 03H 

ROR BL, CL 

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RCL Instruction : RCL destination, count 

This instruction rotates all bits in a specified byte or word some number of bit positions to the left along with the carry flag. MSB is placed as a new carry and previous carry is place as new LSB. 

Eg. RCL CX, 1 

MOV CL, 04H 

RCL AL, CL 

RCR Instruction : RCR destination, count 

This instruction rotates all bits in a specified byte or word some number of bit positions to the right along with the carry flag. LSB is placed as a new carry and previous carry is place as new MSB. 

Eg. RCR CX, 1 

MOV CL, 04H 

RCR AL, CL 

ROR Instruction : ROR destination, count 

This instruction rotates all bits in a specified byte or word to the right some number of bit positions. LSB is placed as a new MSB and a new CF. 

Eg. ROR CX, 1 

MOV CL, 03H 

ROR BL, CL 

RCL Instruction : RCL destination, count 

This instruction rotates all bits in a specified byte or word some number of bit positions to the left along with the carry flag. MSB is placed as a new carry and previous carry is place as new LSB. 

Eg. RCL CX, 1 

MOV CL, 04H 

RCL AL, CL 

RCR Instruction : RCR destination, count 

This instruction rotates all bits in a specified byte or word some number of bit positions to the right along with the carry flag. LSB is placed as a new carry and previous carry is place as new MSB. 

Eg. RCR CX, 1 

MOV CL, 04H 

RCR AL, CL 

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