Send string char by char between two process using fork

I have this assignment where I have to create a program on C/C++ for linux, where it sends a string char by char from one process to another, and when the second process receives the characters it uppercase them.

This is the code I wrote, if someone can tell me if the sharing process is done right or I'm missing something.

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

int main(int argc, char *argv[]) {
    int childpid;
    char *string = "Hello";
    char *letter;

    childpid = fork();

    if(childpid == 0) {
        for (int i = 0; i<string.length; i++) {
            letter = string[i];
            printf(letter);
        }
    } else {
        read(letter);
        printf(letter.toupper());
    }

    return 0;
}

Code update:

#include <stdio.h>
#include <string.h>
#include <ctype.h>
#include <unistd.h>

int main(int argc, char *argv[]) {
    pid_t pid;
    int mypipe[2];
    int ret;
    char *string = "Hello";
    char *buf[20];
    int bytesread;

    ret = pipe(mypipe);

    if(ret == -1) {
        perro("Pipe failed");
        exit(1);
    }

    pid = fork();

    if(pid == 0) {
        for(var i = 0; i<string.length; i++) {
            write(mypipe[1],string[i],1);
        }
    } else {
        while( (bytesread = read(mypipe[0],buf,15)) > 0) 
        {
            buf[bytesread] = '\0';
            printf("buf: %s\n", buf.toupper()); 
        }
    }

    return 0;
}