Under Windows 3.x, the usual method of opening and closing a file consists of calling the same fopen and fclose procedures used under DOS:
hFil = fopen( szFName, “r+b” ); // 3.x
if( hFil != -1 )
{
FilSz = filelength( fileno( hFil ) );
...
fclose( hFil );
}In addition to opening and closing the file in this fragmentary example, the filelength function is also invoked to return the file size. This also should be a familiar function both from Windows 3.1 and from DOS applications, but it changes almost beyond recognition in its Windows 98/95/NT counterpart.
In the Windows 98/95/NT revision, which follows, very little has remained the same. The hFil variable is still used to retrieve a handle to the file opened, but virtually everything else is different.
hFil = OpenFile( szFName, &FileBuff, // 98/95/NT
OF_CANCEL | OF_PROMPT | OF_READ );
if( hFil != -1 )
{
FilSz = GetFileSize( (HANDLE) hFil, &FilSzHigh );
...
_lclose( hFil );
}As you can see, the fopen procedure has been replaced by the OpenFile API call, which uses a quite different selection of parameters. One of these parameters is a pointer to the FileBuff structure, which receives information about the file.
The GetFileSize function is also a major change from its predecessor, filelength. Instead of returning a long value with the file size in bytes, GetFileSize returns two DWORD values: FilSz and FilSzHigh. The reason for this particular change is simple: A signed long value can only report a file size up to about 2GB, but a signed double DWORD value (64 bits) can handle really large file sizes—up to 1.7 × 10308 bytes. Granted, it may be a year or two before mass-storage facilities provide any real need for reporting files of such size, but it will happen eventually.
The final difference—changing fclose to _lclose—is almost no change at all.
NOTE
There is no CloseFile instruction corresponding to the OpenFile API. Instead, the _lclose function is normally used to close a file.
Alternately, instead of using the _lclose instruction, the CloseHandle function can also be used to close files:
hFil = OpenFile( szFName, &FileBuff, // 98/95/NT
OF_CANCEL | OF_PROMPT | OF_READ );
if( hFil != -1 )
{
FilSz = GetFileSize( (HANDLE) hFil, &FilSzHigh );
...
CloseHandle( hFil );
}But opening and closing files are only one aspect of file operations. The previously familiar directory operations have also changed, although perhaps not as drastically.