prnstr macro msg
        mov ah, 09h
        lea dx, msg
        int 21h
        endm

data segment
        hex db 5
            db 0
            db 5 dup(0)
        ans db 17 dup(' ')
        buf1 db "Enter the hexadecimal nmber : $"
        buf2 db 0ah, "The equivalent binary value is : $"
        buf3 db 0dh, 0ah, "Invalid hexadecimal value...$"
        multiplier db 10h
data ends

code segment
        assume cs:code, ds:data
start :
        mov ax, data
        mov ds, ax
        mov es, ax

        prnstr buf1

        mov ah, 0ah
        lea dx, hex
        int 21h

        mov si, offset hex + 2
        mov cx, 0000h
        mov cl, byte ptr [si-1]
subtract :
        mov al, byte ptr [si]
        cmp al, 41h
        jb numb
        cmp al, 47h
    jb cont1
        prnstr buf3
        jmp stop
cont1 :
        sub al, 41h
        add al, 0ah
        jmp cont2
numb :
        cmp al, 30h
        jnb cont3
        prnstr buf3
        jmp stop
cont3 :
        cmp al, 3ah
        jb cont4
        prnstr buf3
        jmp stop
cont4:
        sub al, 30h
cont2 :
        mov byte ptr [si], al
        inc si
        loop subtract

        mov ax, 0000h
        mov si, offset hex + 2
        mov cl, byte ptr [si-1]
loop1 :
        mul multiplier
        mov bl, byte ptr [si]
        mov bh, 00h
        add ax, bx
        inc si
        loop loop1

        mov bx, ax
        mov ax, 8000h
        mov di, offset ans
        mov dx, 0000h
next1 :
        mov cx, 0000h
next2 :
        cmp bx, ax
        jb cont
        sub bx, ax
        inc cx
        jmp next2
cont :
        add cx, 30h
        mov byte ptr [di], cl
        inc di
        mov cx, 0002h
        div cx
        cmp ax, 0000h
        jnz next1

        mov byte ptr [di], '$'
        prnstr buf2
        prnstr ans
stop :
        mov ax, 4c00h
        int 21h
code ends
        end start