x86-64 Linux

int main() {
    __asm__ volatile (
        "syscall"
        :
        : "a" (1),
          "D" (1),
          "S" ("Ciallo World!\n"),
          "d" (14)
        : "rcx", "r11", "memory"
    );
    
    __asm__ volatile (
        "syscall"
        :
        : "a" (60),
          "D" (0)
        : "rcx", "r11", "memory"
    );
}

#include<bits/stdc++.h>
using namespace std;
int main()
{
    cout<<"Ciallo World!";
    return 0;
}