isTwoPower

Very simple and elegant function to test if a number is a power of two.

int isTwoPower(int n){
     if( n < 1 )
         return 0;
     return !(n & (n-1));
}

Hello World!

.data
hello:
   .ascii "Hello World!\n"
   len = . - hello
.text
   .global _start
_start:
   movl $4,     %eax
   movl $1,     %ebx
   movl $hello, %ecx
   movl $len,   %edx
   int $0x80

   movl $1, %eax
   movl $0, %ebx
   int $0x80