procedure

%macro print 2
 mov rax,1
 mov rdi,1
 mov rsi,%1
 mov rdx,%2
 syscall
%endmacro

%macro exit 0
 mov rax,60
 mov rdi,0
 syscall
%endmacro

section .bss
 char_ans resb 2

section .text
 global _start

_start:
 mov rax, 20
 call display
 exit

display:
 mov rbx, 16
 mov rcx, 2
 mov rsi,char_ans+1

back:
 mov rdx, 0

div rbx; rax/rbx

cmp dl, 09h
jbe add30
add dl, 07h

add30:
 add dl, 30h

mov[rsi], dl
dec rsi
dec rcx
jnz back

print char_ans, 2
ret