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Synopsis:
    #include <stdio.h>
    FILE *fopen( const char *filename, const char *mode );

Description:
    The fopen function opens the file whose name is the string pointed to by
    filename, and associates a stream with it.  The argument mode points to
    a string beginning with one of the following sequences:

    "r"
        open file for reading; use default file translation

    "w"
        create file for writing, or truncate to zero length; use default
        file translation

    "a"
        append:  open text file or create for writing at end-of-file; use
        default file translation

    "rb"
        open binary file for reading

    "rt"
        open text file for reading

    "wb"
        create binary file for writing, or truncate to zero length

    "wt"
        create text file for writing, or truncate to zero length

    "ab"
        append; open binary file or create for writing at end-of-file

    "at"
        append; open text file or create for writing at end-of-file

    "r+"
        open file for update (reading and/or writing); use default file
        translation

    "w+"
        create file for update, or truncate to zero length; use default file
        translation

    "a+"
        append; open file or create for update, writing at end-of-file; use
        default file translation

    "r+b", "rb+"
        open binary file for update (reading and/or writing)

    "r+t", "rt+"
        open text file for update (reading and/or writing)

    "w+b", "wb+"
        create binary file for update, or truncate to zero length

    "w+t", "wt+"
        create text file for update, or truncate to zero length

    "a+b", "ab+"
        append; open binary file or create for update, writing at
        end-of-file

    "a+t", "at+"
        append; open text file or create for update, writing at end-of-file

    When default file translation is specified, the value of the global
    variable  _fmode establishes whether the file is to treated as a binary
    or a text file.  Unless this value is changed by the program, the
    default will be text mode.

    Opening a file with read mode ('r' as the first character in the mode
    argument) fails if the file does not exist or it cannot be read.
     Opening a file with append mode ('a' as the first character in the mode
    argument) causes all subsequent writes to the file to be forced to the
    current end-of-file, regardless of previous calls to the  fseek
    function.  When a file is opened with update mode ('+' as the second or
    third character of the mode argument), both input and output may be
    performed on the associated stream.

    When a stream is opened in update mode, both reading and writing may be
    performed.  However, writing may not be followed by reading without an
    intervening call to the  fflush function or to a file positioning
    function ( fseek,  fsetpos,  rewind).  Similarly, reading may not be
    followed by writing without an intervening call to a file positioning
    function, unless the read resulted in end-of-file.

Returns:
    The fopen function returns a pointer to the object controlling the
    stream.  This pointer must be passed as a parameter to subsequent
    functions for performing operations on the file.  If the open operation
    fails, fopen returns NULL.  When an error has occurred,  errno contains
    a value indicating the type of error that has been detected.

See Also:
    fclose, fcloseall, fdopen, freopen, _fsopen

Example:
    #include <stdio.h>

    void main()
      {
        FILE *fp;

        fp = fopen( "report.dat", "r" );
        if( fp != NULL ) {
          /* rest of code goes here */
          fclose( fp );
        }
      }

Classification:
    ANSI, ('t' is a WATCOM extension)

Systems:
    All