Question

MASM Assembly Language programming question. I'm having serious issues. I am attempting to scan through a string and replace all the "o" characters with an exclamation mark (!). However my program does not work and no change seems to occur to the string. Also the loop breaks once the first "o" character is encountered.Is there anyone in this Universe that can help me???Please

main PROC

   ;mov edi,OFFSET string
   mov ecx, LENGTHOF string
   mov edi,OFFSET string
  
L1:

   mov eax,0
   ;mov al,BYTE PTR [edi]
   mov al,[edi]
   cmp al,"o"
   jz Change
   inc edi
   loop L1
  
Change:

   mov eax,0
   mov al,"!"
   call DumpRegs
   mov edi,eax
  

   inc edi
  
  
      
      
      
          
Final:
       mov edx,OFFSET string  
       call WriteString
      

Answer 1

Note:- I had made the required changed and kept in BOLD format. The reason it is not replacing because in Change function ; you were not looping the control back and after change it is going to FINAL label and closing the program. The CHANGE function should be written at the end of the program

MASM PROGRAM :-

main PROC

;mov edi,OFFSET string
mov ecx, LENGTHOF string
mov edi,OFFSET string

mov ebx, 0

L1:

mov eax,0
mov bl, 111
;mov al,BYTE PTR [edi]
mov al,[edi]
cmp al,bl
jz Change
inc edi
loop L1
  
Final:
mov edx,OFFSET string
call WriteString
     
Change:
mov eax,0
mov al,"!"
call DumpRegs
mov [edi],al

inc edi
loop L1