PRB: Network Drive Type Reported Incorrectly

ID: Q75535

The information in this article applies to:

Microsoft Windows Device Development Kit (DDK) for Windows, versions 3.0, 3.1

SYMPTOMS

In versions 3.0 and 3.1 of the Microsoft Windows graphical environment, the Windows File Manager and the GetDriveType() API reports that some network drives are local fixed drives.

CAUSE

In some releases of PC-DOS version 4.00 and MS-DOS version 4.01, Interrupt 21h Function 4409h does not reliably return drive type information.

RESOLUTION

The redirection entry list must store the local drive name in uppercase letters.

MORE INFORMATION

To work around the Interrupt 21h Function 4409h problem, Windows 3.0 or 3.1 recognizes that it is running on PC-DOS 4.00 or MS-DOS 4.01 and uses Interrupt 21h Function 5F02h (Get Redir List Entry) to determine if a drive is remote or local. Windows compares the drive index (A = 0, B = 1, ..., Z = 25) to the drive index returned by the function. Windows also assumes that the drive letter is uppercase.

If lpszLocal points to the "local" name returned by Get Redir List Entry, Windows uses the following algorithm:


     if ((lpszLocal[0] - 0x41) == wListIndex)
    {
        /** drive is remote **/ 
    }

    else
    {
        /** drive is fixed **/ 
    }

Therefore, if the redirection entry list does not store the local name in uppercase letters, and Windows 3.0 or 3.1 is running under PC-DOS 4.00 or MS-DOS 4.01, then the network drive will be reported as being "FIXED."

Additional query words: 3.00 3.10 VXDTSR

Keywords :
Version : :3.0,3.1
Platform :
Issue type :