file pointer and file descriptor in c

fd_fp.c

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

int main(int argc, char const *argv[])
{
    char str[] = "Hello World !!!";
    int fd = fileno(stdout);
    FILE *fp = fdopen(fd, "w");
    fwrite(str, sizeof(char), sizeof(str), fp);
    return 0;
}