%macro scall 4
    mov rax,%1
    mov rdi,%2
    mov rsi,%3
    mov rdx,%4
    syscall
%endmacro

section .data
    m1 db 10,"Enter 4 digit Hex no.:"
    l1 equ $-m1

    m2 db 10,13,"Equivalent BCD number is:"
    l2 equ $-m2

section .bss
    buf resb 6
    digitcount resb 1
    char_ans resb 4

section .text
    global _start

_start:
    scall 1,1,m1,l1
    scall 0,0,buf,5

    call accept_proc
    mov ax,bx
    call h2bproc

;---------------exit--------------------
    mov rax,60
    mov rdi,0
    syscall

;----------------HEX to BCD-----------------
h2bproc:
    mov rbx,0Ah
back:
    xor rdx,rdx
    div rbx
    push dx 
    inc byte[digitcount]
    cmp rax,0h
    jne back
    scall 1,1,m2,l2
print_bcd:
    pop dx
    add dl,30h
    mov [char_ans],dl
    scall 1,1,char_ans,1
    dec byte[digitcount]
    jnz print_bcd
ret

;------------------accept procedure----------------
accept_proc:
    mov bx,0000h
    mov ax,0000h
    mov rcx,4
    mov rsi,buf
nextdigit:
    rol bx,4
    mov al,[rsi]
    cmp al,39h
    jbe label1
    sub al,07h
label1:
    sub al,30h
    add bx,ax
    inc rsi
    dec rcx
    jnz nextdigit
ret