capitalreversesmall.asm

converts capital to small letters

.MODEL SMALL
.STACK 100H

.DATA
   PROMPT_1  DB  'Please Enter Capital letters: $'
   DISPLAY_1  DB  0DH,0AH,'Small letters in reverse order: $'
   LETTERS DB ?

.CODE
   MAIN PROC
     MOV AX, @DATA          ; initialize DS  
     MOV DS, AX

     LEA DX, PROMPT_1       ; load and display PROMPT_1  
     MOV AH, 9
     INT 21H


     XOR SI,SI             ; SET SI TO 0
     MOV CX,5              ; initialize loop counter
     MOV AH, 1              ; set input function

     CONVERT:               ; jump label
       INT 21H              ; read a digit
      
       ADD AL,20H
       MOV AL,LETTERS[SI]
       ADD SI,1            ; move pointer to next element by 1(DB)
      
       LOOP CONVERT         ; jump to label INPUT
      
       LEA DX, DISPLAY_1       ; load and display PROMPT_1  
       MOV AH, 9
       INT 21H
      
        ;display character function
    MOV AH,2

    REVERSE:
    MOV DL,LETTERS[SI];move last element to DL
    INT 21H        ;display character
    SUB SI,1
    CMP SI,0
        JE EXIT
         LOOP REVERSE         ; jump to label INPUT     ;display character
    
      

    EXIT:
             MOV AH, 4CH             ; return control to DOS
             INT 21H
  
    MAIN ENDP
    END MAIN