## hello-world.s

        ## by Robin Miyagi
        ## http://www.geocities.com/SiliconValley/Ridge/2544/

        ## Compile Instructions:
        ## -------------------------------------------------------------
        ## as -o hello-world.o hello-world.s
        ## ld -o hello-world -O0 hello-world.o

        ## This  file is  a basic  demonstration of  the  GNU assembler,
        ## `as'.
        
        ## This program  displays a friendly string on  the screen using
        ## the write () system call
########################################################################
        .section .data
hello:  
        .ascii  "Hello, world!\n"
hello_len:
        .long   . - hello
########################################################################
        .section .text
        .globl _start
        
_start:
        ## display string using write () system call
        xorl %ebx, %ebx         # %ebx = 0
        movl $4, %eax           # write () system call
        xorl %ebx, %ebx         # %ebx = 0
        incl %ebx               # %ebx = 1, fd = stdout
        leal hello, %ecx        # %ecx ---> hello
        movl hello_len, %edx    # %edx = count
        int $0x80               # execute write () system call
        
        ## terminate program via _exit () system call 
        xorl %eax, %eax         # %eax = 0
        incl %eax               # %eax = 1 system call _exit ()
        xorl %ebx, %ebx         # %ebx = 0 normal program return code
        int $0x80               # execute system call _exit ()