ID: Q105922
3.10 WINDOWS kbprg
The information in this article applies to:
The Windows versions 3.0 and 3.1 GetDriveType() function is useful for determining whether a given drive is on a network or uses fixed or removable media, but does not determine the specific type of device that is associated with the drive. This article presents a function, GetDriveTypeEx(), that can determine whether a given drive exists and whether it is one of the following types of devices:
Hard disk drive
RAM disk drive
CD-ROM drive
Floppy disk drive
Remote network drive
Other removable media drive (such as a Bernoulli box)
UINT GetDriveTypeEx(int nDrive); // 0=A, 1=B, 2=C, etc.
EX_DRIVE_REMOVABLE EX_DRIVE_FIXED
EX_DRIVE_REMOTE EX_DRIVE_CDROM
EX_DRIVE_FLOPPY EX_DRIVE_RAMDISK
EX_DRIVE_INVALID
The Windows 32-bit API version of the GetDriveType() function determines whether a drive is a RAM disk or a CD-ROM in addition to categorizing the drive as either removable media, fixed media, or remote. See the Microsoft Win32 SDK for further information about how to use GetDriveType() in Win32 applications and DLLs.
GetDriveTypeEx() works by first calling the Windows GetDriveType() function to categorize the drive as being either fixed, removable, remote (network), or not present. If the drive is remote, it could be either a CD-ROM drive or a network drive because CD-ROM drives are mapped by the MS-DOS network redirector. The best way to determine whether a drive is a CD-ROM drive is to call the Microsoft CD-ROM Extensions (MSCDEX) CD-ROM Drive Check function.
If the drive uses fixed media, it could be either a hard disk or a RAM disk. A good way to determine whether the drive is a hard disk is to call the MS-DOS Get Device Parameters IOCTL function and then check the device type byte in the returned structure. If the drive is not a hard disk, it can be assumed to be a RAM disk because these are the only two fixed media devices.
Finally, if the drive uses removable media, it could be a floppy disk drive or some other device, such as a Bernoulli box. The MS-DOS Get Device Parameters IOCTL function can be used to determine whether the drive is a floppy disk drive; if it is not, it could be a Bernoulli box or some other less common device.
The following code for Microsoft C compilers implements GetDriveTypeEx() and its support functions and all required structures:
#include <windows.h>
#include <string.h>
// Return values of GetDriveTypeEx().
#define EX_DRIVE_INVALID 0
#define EX_DRIVE_REMOVABLE 1
#define EX_DRIVE_FIXED 2
#define EX_DRIVE_REMOTE 3
#define EX_DRIVE_CDROM 4
#define EX_DRIVE_FLOPPY 5
#define EX_DRIVE_RAMDISK 6
// See the "MS-DOS Programmer's Reference" for further information
// about this structure.
{
BYTE bSpecFunc; // Special functions
BYTE bDevType; // Device type
WORD wDevAttr; // Device attributes
WORD wCylinders; // Number of cylinders
BYTE bMediaType; // Media type
// Beginning of BIOS parameter block (BPB)
WORD wBytesPerSec; // Bytes per sector
BYTE bSecPerClust; // Sectors per cluster
WORD wResSectors; // Number of reserved sectors
BYTE bFATs; // Number of FATs
WORD wRootDirEnts; // Number of root-directory entries
WORD wSectors; // Total number of sectors
BYTE bMedia; // Media descriptor
WORD wFATsecs; // Number of sectors per FAT
WORD wSecPerTrack; // Number of sectors per track
WORD wHeads; // Number of heads
DWORD dwHiddenSecs; // Number of hidden sectors
DWORD dwHugeSectors; // Number of sectors if wSectors == 0
// End of BIOS parameter block (BPB)
} DEVICEPARAMS, FAR * LPDEVICEPARAMS;
// Function prototypes
//-----------------------------------------------------------------
// GetDeviceParameters()
//
// Fills a DEVICEPARAMS struct with info about the given drive.
// Calls DOS IOCTL Get Device Parameters (440Dh, 60h) function.
//
// Parameters
// nDrive Drive number 0 = A, 1 = B, 2 = C, and so on.
// dp Pointer to a structure that will contain the drive's
// parameters.
//
// Returns TRUE if it succeeded, FALSE if it failed.
//-----------------------------------------------------------------
{
BOOL bResult = TRUE; // Assume success
__asm {
push ds
mov bx, nDrive
inc bx // Convert 0-based #'s to 1-based #s
mov ch, 08h // Device category--must be 08h
mov cl, 60h // MS-DOS IOCTL Get Device Parameters
lds dx, dp
mov ax, 440Dh
int 21h
jnc gdp_done // CF SET if error
mov bResult, FALSE
gdp_done:
pop ds
}
return (bResult);
}
//-----------------------------------------------------------------
// IsCDRomDrive()
//
// Determines if a drive is a CD-ROM. Calls MSCDEX and checks
// that MSCDEX is loaded, and that MSCDEX reports the drive is a
// CD-ROM.
//
// Parameters
// nDrive Drive number 0 = A, 1 = B, 2 = C, and so forth.
//
// Returns TRUE if nDrive is a CD-ROM drive, FALSE if it isn't.
//-----------------------------------------------------------------
{
BOOL bResult = FALSE; // Assume not a CD-ROM drive
__asm {
mov ax, 150Bh // MSCDEX CD-ROM Drive Check
xor bx, bx
mov cx, nDrive
int 2Fh
cmp bx, 0ADADh // Check MSCDEX signature
jne not_cd_drive
or ax, ax // Check the drive type
jz not_cd_drive // 0 (zero) means not CD-ROM
mov bResult, TRUE
not_cd_drive:
}
return (bResult);
}
//-----------------------------------------------------------------
// GetDriveTypeEx()
//
// Determines the type of a drive. Calls Windows's GetDriveType
// to determine if a drive is valid, fixed, remote, or removeable,
// then breaks down these categories further to specific device
// types.
//
// Parameters
// nDrive Drive number 0 = A, 1 = B, 2 = C, etc.
//
// Returns one of:
// EX_DRIVE_INVALID -- Drive not detected
// EX_DRIVE_REMOVABLE -- Unknown removable-media type drive
// EX_DRIVE_FIXED -- Hard disk drive
// EX_DRIVE_REMOTE -- Remote drive on a network
// EX_DRIVE_CDROM -- CD-ROM drive
// EX_DRIVE_FLOPPY -- Floppy disk drive
// EX_DRIVE_RAMDISK -- RAM disk
//-----------------------------------------------------------------
{
DEVICEPARAMS dp;
UINT uType;
_fmemset (&dp, 0, sizeof(dp)); // Init device params struct
uType = GetDriveType (nDrive);
switch (uType)
{
case DRIVE_REMOTE:
// GetDriveType() reports CD-ROMs as Remote drives. Need
// to see if the drive is a CD-ROM or a network drive.
if (IsCDRomDrive (nDrive))
return (EX_DRIVE_CDROM);
else
return (EX_DRIVE_REMOTE);
break;
case DRIVE_REMOVABLE:
// Check for a floppy disk drive. If it isn't, then we
// don't know what kind of removable media it is.
// For example, could be a Bernoulli box or something new...
if (GetDeviceParameters (nDrive, &dp))
switch (dp.bDevType)
{
// Floppy disk drive types
case 0x0: case 0x1: case 0x2: case 0x3:
case 0x4: case 0x7: case 0x8:
return (EX_DRIVE_FLOPPY);
}
return (EX_DRIVE_REMOVABLE); // Unknown removable media type
break;
case DRIVE_FIXED:
// GetDeviceParameters returns a device type of 0x05 for
// hard disks. Because hard disks and RAM disks are the two
// types of fixed-media drives, we assume that any fixed-
// media drive that isn't a hard disk is a RAM disk.
if (GetDeviceParameters (nDrive, &dp) && dp.bDevType == 0x05)
return (EX_DRIVE_FIXED);
else
return (EX_DRIVE_RAMDISK);
break;
}
return (EX_DRIVE_INVALID); // Drive is invalid if we get here.
}
Last Reviewed: July 24, 1997