Do the standard streams all operate on the same file (/dev/tty)?

If I type ls -l /dev in a virtual terminal I get

lrwxrwxrwx 1 root root 15 apr 10 10:59 stderr -> /proc/self/fd/2 lrwxrwxrwx 1 root root 15 apr 10 10:59 stdin -> /proc/self/fd/0 lrwxrwxrwx 1 root root 15 apr 10 10:59 stdout -> /proc/self/fd/1 

If i then type ls -l /proc/self/fd I get

lrwx------ 1 user user 64 apr 10 19:59 0 -> /dev/pts/1 lrwx------ 1 user user 64 apr 10 19:59 1 -> /dev/pts/1 lrwx------ 1 user user 64 apr 10 19:59 2 -> /dev/pts/1 

All entries point to the same device file, which also happen to be the controlling terminal for the virtual shell (as confirmed by the "tty" command). Am I then right to assume that the stdin, sdout and stderr file descriptors all operate on the same file (/dev/pts/1), e.g. three separate open() calls have been made (when the virtual shell process was forked from its parent process) on the same file?

If so, while running the following program:

#include <fcntl.h> #include <unistd.h> #include <stdio.h> int main() { int rfd = open("./a_file",O_RDONLY); int wfd = open("./a_file",O_WRONLY); char rc='a',wc='b'; if (write(rfd,&wc,1)<0) { perror("Error"); } if (read(wfd,&rc,1)<0) { perror("Error"); } } 

Gives:

Error: Bad file descriptor Error: Bad file descriptor 

As expected, but when changing rfd to 1 (sdtout) and wfd to 0 (stdin) in the read() arguments, I don't get an error. Does this mean that /dev/tty was opened with the O_RDWR flag?

When trying:

if (write(1,&wc,1)<0) { perror("Error"); } if (read(0,&rc,1)<0) { perror("Error"); } 

I see the 'b' on the console, but the read() call doesn't return, as if there wasn't any data to be read from the file. Why is that?