Lab 8 - 60-266-implement binary multiplication using arithmetic shift and add operations using assembly

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Lab 8 – 60-266-implement binary multiplication using arithmetic shift and add operations using assembly

OBJECTIVES:
i) Understand binary multiplication.
ii) To learn to implement binary multiplication using arithmetic shift and add operations.
iii) To learn to access and manipulate bits using various shift/rotate operations

Problem: a) Multiply a 16-bit unsigned integer (03B2 h) by 12 using arithmetic shift and add operations. The result should be in register ax.
b) Move the most significant 4 bits of ax into the least significant 4 bits of bx. The most significant 4 bits of bx as well as the contents of ax should remain unchanged.

Hints:

• Multiplying a number by 2n is equivalent to shifting it to the left n times.
• 12 = 8 + 4 = 23 + 22
• Not discussed in class: The SHLD instruction can be used to perform a shift operation without modifying the source.
o Students can use SHL however.

Answer:

INCLUDE Irvine32.inc .code main PROC ; Part a) mov bx, 03b2h ; Initialize bx to the value ; to be multiplied call dumpregs ; Display the content of regs shl bx, 3 ; shift bl to the left 3 times. ; Result of this operation is ; equivalant to the value ; of bx multiplied by 2^3. mov ax, bx ; Save bx for future use call dumpregs ; display the content of regs mov bx, 03b2h ; Initialize bx to the value ; of the multiplicand call dumpregs ; display the content of regs shl bx, 2 ; shift bl to the left 2 times. ; Result of this operation is ; equivalant to the value ; of bx multiplied by 2^2. call dumpregs ; display the content of regs add ax, bx ; Add the value of bx to ax. Now, ax ; contains the result of the multiplication. ; for part (a) call dumpregs ; display the content of regs ; Part b) mov bx, 3467h ; For part (b), re-initialize ; the value of bx just to test ; that the move operation is working ; properly. call dumpregs ; display the content of regs shr bx, 4 ; Shift bx to the right so that after ; the shld operation, the content of the ; 12 most significant bits of bx remains same. call dumpregs ; display the content of regs shld bx, ax, 4 ; This operation shifts bx to the left ; by 4 bits, then replaces the least 4 ; significant 4 bits of bx by the most ; significant 4 bits of ax call dumpregs ; display the content of regs exit main ENDP END main