Calling System Call Directly

#include <stdio.h>
#include <stdlib.h>
#include <sys/syscall.h>
#include <unistd.h>
 
int myadd(int a,int b)
{
    int res;
    asm volatile ("movl $320,%%eax; movl %1,%%ebx; movl %2,%%ecx;int $0x80; movl %%eax,%0;":
            "=r"(res): "r"(a),"r"(b) : "eax","ebx","ecx");
    return res;
}
 
int main(void) {
    int x=9,y=8,z;
    puts("!!!Hello World!!!"); /* prints !!!Hello World!!! */
    //z=syscall(320,x,y);
    z=myadd(x,y);
    printf("res=%d\n",z);
    return EXIT_SUCCESS;
}