Fooling around with nasm

sum.asm

; /usr/local/bin/nasm -f macho64 sum.asm && ld -macosx_version_min 10.7.0 -lSystem -o sum sum.o && ./sum

global start


section .text
extern _printf
extern _exit

start:
	; Calculations
	mov rax, 1
	push rax
	mov rax, 2
	pop rbx
	add rax, rbx
	push rax
	mov rax, 3
	pop rbx
	add rax, rbx
	push rax
	mov rax, 9
	pop rbx
	add rax, rbx

	
	; Output
	mov rsi, rax					; Move result to output
	
	
	mov qword   rax, 0                              ;A zero in rax indicates that printf receives standard 
	lea         rdi, [rel message]
	call        _printf
	mov qword   rax, 0
	call		_exit

section .data

message: db "Register %i", 10, 0
.len:   equ     $ - message