CS 111

CS 206D Computer OrganizationLab3

CS 111

LOOP Instruction • The LOOP instruction can be used to implement a for loop.

• Syntax:

; initialize CX to loop_count destnation_lable:

; body of the loopLOOP destnation_lable

CS 111

LOOP instruction

• The counter for the loop is the register CX, which is initialized to loop_count.

• Execution of the LOOP instruction causes CX to be decremented automatically.

• If (CX < > 0) control transfers to destination_label else the next instruction after LOOP is done.

For loop

CS 111

• Example: Write some code to display a row of 20 stars.

• Solution: Pseudo code:

FOR 20 times DO display '*'END_IF

For loop

CS 111

• Example: Write some code to display a row of 20 stars.

It can be coded as follows:MOV CX, 20 ; initialize CX to 80MOV AH, 2MOV DL, '*'

TOP:INT 21hLOOP TOP

Exercise :

CS 111

• Example: Write some code to display all English alphabets (A TO Z)

Exercise :

CS 111

• Example: Write some code to display all English alphabets (A TO Z)