what am i missing here??

Here's a code i wrote to find out how non-blocking read works...

Code:

int main()
{
        int fd;
        int n;
        char buf[1024];
        char ch;

        fd = open("/dev/tty", O_RDWR | O_NONBLOCK);
        if (fd == -1) {
                perror("open");
                exit(EXIT_FAILURE);
        }

        while ((n = read(fd, buf, 1024)) != 0) {
                if (n == -1) {
                        if (errno == EAGAIN) {
                                printf("no data\n", n);
                                sleep(2);
                        }
                }
                else {
                        buf[n] = '\0';
                        printf("read %s\n", buf);
                        break;
                }
        }
        exit(0);
} 

the thing is that i cannot really determine how this read works. just typing on the terminal doesn't make the read return and it keeps on returning -1 with errno = EAGAIN.
the data from the terminal is read only on hitting enter. so why is that needed. how can i get the tty to work like a normal file with read.

thanks