The stdin, stdout and stderr FILE type Pointers

The stdin, stdout and stderr are names used to refer to the standard input device (keyboard) and standard output and error device (VDU). These are actually FILE type pointers, defined in the file stdio.h, and can be used with file input-output functions.

For example, the following statement:

fputc (c, stdout);

writes the value of the char type variable c onto the VDU.

The standard input, output and error files are not opened within C programs, since the operating system makes these devices available for all programs.