Question

Use 25 to 50 words to discuss one of the Shift, Rotate, Multiplication, Division Instructions and give a simple example of the .asm complete program code that you have compiled. Just keep the code simple with not much program description. Put your code in a program and make sure it compiles then copy it.  Do some research, using articles other than your textbook would be great also.

Answer 1

Shift Instructions:

In Assembly Language there are 5 shift instructions, these instructions are used to move the bits in a register left or right by a specified number of bits, called shift length.

Register shift can be performed:

Directly by the instructions ASR, LSR, LSL, ROR, and RRX, and the result is written to a destination register.

During the calculation of Operand2 by the instructions that specify the second operand as a register with shift. The result is used by the instruction.

Arithmetic shift right (ASR)

Arithmetic shift right by m bits moves the left-hand 32-m bits of a register to the right by n places, into the right-hand 32-m bits of the result.

Logical shift right (LSR)

Logical shift right by m bits moves the left-hand 32-m bits of a register to the right by m places, into the right-hand 32-m bits of the result. It sets the left-hand n bits of the result to 0.

Logical shift left (LSL)

Logical shift left by m bits moves the right-hand 32-m bits of a register to the left by m places, into the left-hand 32-m bits of the result. It sets the right-hand m bits of the result to 0.

Rotate right (ROR)

Rotate right by m bits moves the left-hand 32-m bits of a register to the right by m places, into the right-hand 32-m bits of the result. It also moves the right-hand m bits of the register into the left-hand m bits of the result.

Rotate right with extend (RRX)

Rotate right with extend moves the bits of a register to the right by one bit. It copies the carry flag into bit[31] of the result.

MULTIPLICATION INSTRUCTION:

In Assembly Language MUL(Unsigned multiplication) & IMUL(Signed multiplication) instructions are used to multiply two 8-,16-,32-bit registers.

Eg:

.DATA

A DW 0FF87H

B DW 0FF84H

C DW ?

.CODE

START:

MOV AX,@DATA

MOV DS,AX

MOV SI,0000H

MOV AX,A

MOV CX,B

MUL CX ; IMUL for signed multiplication

INT 03H

END START

DIVISION INSTRUCTION:

In Assembly Language DIV(Unsigned division) & IDIV(Signed division) instructions are used to divide two 8-,16-,32-bit registers.

Eg:

.DATA

A DW 0FF87H

B DW 0FF84H

C DW ?

.CODE

START:

MOV AX,@DATA

MOV DS,AX

MOV SI,0000H

MOV AX,A

MOV CX,B

DIV CX ;IDIV for signed division

INT 03H

END START