Loop loop and CX

Example ： Calculation 2 Of 12 Power

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        assume cs:code
        
code segment
        
start:
        
  mov ax,2
        
  mov cx,11
        
s:  add ax,ax
        
  loop s
        
  mov ax,4c00h
        
  int 21h
        
code ends
        
end start
       
       

        
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cx Program counter （countRegister Abbreviation ） perform loop When you cycle, you will first cx-1, And judge cx Is it equal to 0, be equal to 0 End cycle , Otherwise, execute the loop body

among mov ax,4c00h Indicates that the program returns dos, Will be in mov ah,4ch take ax The high order of is assigned to 4c That means return dos

​int  yes interupt Short for interrupt ​

int 21h Express , interrupt , To carry out 4c Instructions , Indicates that the program ends with a return code .