8086 LOOP Instruction Edit
Loop instruction is a Transfer Of Control Instruction in 8086 assembly language. Loop instructin transfers the control to a specific label or jumps to specific label If CX is not equal to zero after auto decrement. Its used for looping though a set of instructions and you can specify the number of times the loop have to execute in the CX register. This instruction does not affect any flag.
Decrease CX, jump to label if CX not zero.
CX = CX - 1 if CX <> 0 then jump else no jump, continue
In the below code we will try to print hello world 10 times
.model tiny .code org 100h main proc near mov cx,10d loop1: push cx ; Best practice, I am pushing the value of cx to the stack and poping it out just ; before the loop instruction, This is done to avoid cx from being modified by ; the set of instructions below between the label loop1 and loop instruction mov ah,09h ; dos function to print a string mov dx,offset message ; memory location of message to print int 21h ; dos interrupt 21h pop cx loop loop1 ; here the value of cx is decremented by 1 and if the value of cx is not zero after decrement then control is transfered to loop1 mov ah,4ch ; dos funcion to terminate and return to dos mov al,00 int 21h ; dos interrupt 21h ret endp message db 'hello world',0ah,0dh,'$' ; string ends with $, 0ah is carriage return, 0dh is line feed end main