Question

Write an assembly program which asks user to enter a character from ‘A’ to ‘Z’. If the user enters any other character, the program asks user to enter the character again. In this way the program inputs 300 characters and stores it in memory location from address $1000 to $112B. Hint: Use CPU register Y as counter

Answer 1

Answer : Given data

.MODEL SMALL
 .STACK 100H

 .DATA
   PROMPT_1  DB  'Enter the character : $'
   PROMPT_2  DB  0DH,0AH,'The ASCII code of the given number in binary form is : $'
   PROMPT_3  DB  0DH,0AH,'The number of 1 bits in ASCII code are : $'

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

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

     MOV AH, 1                    ; read a character
     INT 21H

     XOR BX, BX                   ; clear BX
     MOV BL, AL                   ; move AL to BL

     LEA DX, PROMPT_2             ; load and display PROMPT_2
     MOV AH, 9
     INT 21H

     XOR BH, BH                   ; clear BH
     MOV CX, 8                    ; initialize loop counter
     MOV AH, 2                    ; set output function

     @OUTPUT:                     ; jump label
       SHL BL, 1                  ; shift left BX by 1 bit

       JNC @ZERO                  ; jump to label @ZERO if CF=0
       INC BH                     ; increment BH
       MOV DL, 31H                ; set DL=1
       JMP @DISPLAY               ; jump to label @DISPLAY

       @ZERO:                     ; jump label
         MOV DL, 30H              ; set DL=0

       @DISPLAY:                  ; jump label
         INT 21H                  ; display digit
     LOOP @OUTPUT                 ; jump to label @OUTPUT

     LEA DX, PROMPT_3             ; load and display the string PROMPT_3
     MOV AH, 9
     INT 21H

     OR BH, 30H                   ; convert the decimal to ascii code

     MOV AH, 2                    ; print the contents of BH
     MOV DL, BH
     INT 21H

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

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