hexa to binary(corrected).asm

.MODEL SMALL
.STACK 100H
.DATA

.CODE
MAIN PROC

    MOV AX,@DATA
    MOV DS,AX

    XOR BX,BX  ;CLEAR BX
    MOV CL,4  ;COUNTER FOR 4 SHIFTS
    MOV AH,1
    INT 21H


    WHILE_:
    CMP AL,0DH  ;CR?
    JE PRINT  ; YES,EXIT


    ;CONVERT CHARACTER TO BINARY VALUE
    CMP AL,39H  ;A DIGIT?
    JG LETTER  ; NO, A LETTER


    ;INPUT IS A DIGIT
    AND AL,0FH  ;CONVERT DIGIT TO BINARY VALUE
    JMP SHIFT   ;GO TO INSERT IN BX



    LETTER:
    SUB AL,37H  ;convert letter to binary

    SHIFT:
    SHL BX,CL

    ;insert value into BX
    OR BL,AL ; put value into low 4 bits

    INT 21H
    JMP WHILE_



    PRINT:
    MOV CX,16

    L1:
    ROL BX,1
    ;JNC L2
    JC L3

    MOV AH,2
    MOV DL,'0'
    INT 21H
    LOOP L1

    JMP EXIT

    L3:
    MOV AH,2
    MOV DL,'1'
    INT 21H
    LOOP L1


    EXIT:
    MOV AH,4CH
    INT 21H
    MAIN ENDP
END MAIN