stdin, stdout and stderr

[Humble]

Everyone heard about it.. How-ever confusion exist on this. I am talking these bits in context of C programming..

When a program starts these 3 are already opened and available for you.. These are IO streams.

In standard header file stdio.h it has been defined as

extern struct _IO_FILE *stdin; /* Standard input stream. */
extern struct _IO_FILE *stdout; /* Standard output stream. */
extern struct _IO_FILE *stderr; /* Standard error output stream. */

stdin   -> This reads input from the terminal and by default it access the keyboard..

stdout  -> This writes output to the terminal and by default it send data to your screen/monitor.

stderr  -> This writes diagnostic/error output to the terminal, by default it write same to stdout.


Where stdin is opened in "r" mode and rest 2 are opened in "w" mode.

Functions like gets() , getchar() reads from stdin.

Functions like fgets(), fgetc(), fscnaf() ..etc can access stdin

Functions like printf(), puts(), putchar() ..etc write/send data to stdout.
  
Functions like  fprintf(), fputs() can use of stderr.

Above mentioned streams (stdin,stdout,stderr)  all use text as the method of I/O.

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