# Ivan Novick
# this program demonstrates how to call printf from assembly using GNU assembler
# on a x86 intel compatible CPU
#
# build command lines
# as -o callprintf.o callprintf.s
# ld -dynamic-linker /lib/ld-linux.so.2 -o callprintf -lc callprintf.o
#
#
# data section we will declare 2 variables an integer and a null-terminated string
.section .data
x:        .int   123456789
mystring: .asciz "The number is: %d\n"

# we right the instructions int the text section
.section .text

# this is how we declare the main function
.globl _start
_start:

# push the 2 arguments to the printf function onto the stack
# arguments are pushed in reverse order, so first the integer and then
# the string, as reverse for how you would type printf in C
# when done pop the parameters off the stack by adding the immediate value 8 to the stack pointer
movl x, %eax
pushl %eax
pushl $mystring
call printf
addl $8, %esp

# exit system call
movl $1, %eax
movl $0, %ebx
int $0x80