hw.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int main(int argc, char **argv)
{
    char *msg = (char *)calloc(13, sizeof(char));
    strcpy(msg, "Hello World!");

    FILE *out = fopen("/dev/stdout", "w");
    fprintf(out, "%s\n", msg);
    fclose(out);

    return 0;
}