stdin
 stdout
 stderr

 NAME
  stdin  - standard input channel (file pointer - MACRO)
  stdout - standard output channel (file pointer - MACRO)
  stderr - standard error channel (file pointer - MACRO)

 SYNOPSIS
  #include <stdio.h>


 FUNCTION
  stdin is a FILE * type that represents the program's standard
  input stream.  This can be redirected via command line redirection
  when the program is run.

  stdout is a FILE * type that represents the program's standard
  output stream.  This can also be redirected via command line
  redirection when the program is run.

  stderr is a FILE * type that represents the program's standard
  error stream.  Currently stderr is openned by _main and represents
  the console device associated with the program regardless of
  standard redirections.

  These file pointers may be fclose()d or freopen()d at any time.
  The stdio macros getchar() and putchar() and stdio library
  routines gets() and puts() deal with stdin and stdout
  respectively while other library routines such as perror() output
  to stderr.

 SEE ALSO
  gets, puts, getchar, putchar, perror