Q11988: Windows File I/O vs. C Run-time File I/O

Article: Q11988
Product(s): Microsoft Windows Software Development Kit
Version(s): WINDOWS:3.0,3.1
Operating System(s): 
Keyword(s): kb16bitonly
Last Modified: 06-NOV-1999

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The information in this article applies to:

- Microsoft Windows Software Development Kit (SDK) versions 3.0, 3.1 
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SUMMARY
=======

The following functions are provided by the Microsoft C Run-time Library (CRT)
and the Windows API to create a file:

  Return Type    API or Function   Category
  --------------------------------------------
  HFILE          OpenFile          Windows API
  HFILE          _lopen/_lcreat    Windows API
  int            _open/_creat      CRT
  FILE *         fopen             CRT

These return types (HFILE, int, and FILE *) are not compatible, so they can not
be used in a function which is expecting the other type. The HFILEs are handles
to operating system files (MS-DOS file handles), the ints are CRT file handles,
and the FILE *s are pointers to structures which represent a CRT stream.

For files opened with OpenFile(), _lopen, and _lcreat, the common file
manipuluation routines that you should use are:

  _lclose
  _llseek
  _lread
  _lwrite

For files opened with _open() and _creat(), the common file manipulation routines
that you should use are:

  _close
  _lseek
  _read
  _write

For files opened with fopen, the common file manipulation routines that you
should use are:

  fclose
  fseek
  fread
  fwrite

For other input and output functions, please check the documentation for
information on whether they are intended for use with MS-DOS handles (HFILE),
streams (FILE *), or low-level I/O (int).

MORE INFORMATION
================

An application should use the OpenFile() API any time an MS-DOS file handle is
required.

The open functions do not necessarily open a file in binary raw mode; the
application is required to set the binary attribute explicitly. The OpenFile()
function automatically performs this step.

If the filename parameter specifies only a filename and extension, the open
functions search for a matching file only in the current directory.

In Windows, the OpenFile() API creates an MS-DOS file handle through which an
application can access Windows-specific files. OpenFile() initially opens the
file in binary raw mode by performing an MS-DOS Interrupt 21h Function 3Dh. If
the lpFileName parameter specifies only a filename and an extension, OpenFile()
searches for a matching file in the following directories:

- The current directory.

- The Windows directory. The GetWindowsDirectory() API returns the path to this
  directory.

- The Windows system directory . The GetSystemDirectory() API returns the path
  to this directory.

- The directories listed in the PATH environment variable.

Additional query words: 3.00 3.10

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Keywords          : kb16bitonly 
Technology        : kbAudDeveloper kbWin3xSearch kbSDKSearch kbWinSDKSearch kbWinSDK300 kbWinSDK310
Version           : WINDOWS:3.0,3.1

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