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

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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 cannot be used in a function which is expecting the other type. The HFILEs arehandles to operating system files (MS-DOS file handles), the ints are CRTfile handles, and the FILE *s are pointers to structures which represent aCRT stream.

For files opened with OpenFile(), _lopen, and _lcreat, the common filemanipuluation routines that you should use are:
_lclose
_llseek
_lread
_lwrite
For files opened with _open() and _creat(), the common file manipulationroutines that you should use are:
_close
_lseek
_read
_write
For files opened with fopen, the common file manipulation routines that youshould use are:
fclose
fseek
fread
fwrite
For other input and output functions, please check the documentation forinformation 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 handleis required.

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

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

In Windows, the OpenFile() API creates an MS-DOS file handle through whichan application can access Windows-specific files. OpenFile() initiallyopens the file in binary raw mode by performing an MS-DOS Interrupt 21hFunction 3Dh. If the lpFileName parameter specifies only a filename and anextension, OpenFile() searches for a matching file in the followingdirectories:

  • 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.
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Article ID: 11988 - Last Review: 12/04/2015 08:54:23 - Revision: 3.0

Microsoft Windows Software Development Kit 3.0, Microsoft Windows Software Development Kit 3.1

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