Untitled

section .text
 global _start ;must be declared for using gcc
_start: ;tell linker entry point
 mov ecx,'4'
 sub ecx, '0'
 mov edx, '5'
 sub edx, '0'
 call sum ;call sum procedure
 mov [res], eax
 mov ecx, msg
 mov edx, len
 mov ebx,1 ;file descriptor (stdout)
 mov eax,4 ;system call number (sys_write)
 int 0x80 ;call kernel
 mov ecx, res
 mov edx, 1
 mov ebx, 1 ;file descriptor (stdout)
 mov eax, 4 ;system call number (sys_write)
 int 0x80 ;call kernel
 mov eax,1 ;system call number (sys_exit)
 int 0x80 ;call kernel
sum:
 mov eax, ecx
add eax, edx
 add eax, '0'
 ret
section .data
msg db "The sum is:", 0xA,0xD
len equ $- msg
segment .bss
res resb 1