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Posted 28 Mar 2004


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How To get the usbdisk's drive letter properly

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28 Mar 2004CPOL2 min read
Using DeviceIoControl to get UsbDisk Drive letter(s)

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We know USB disk should be a removable disk just like floppy disk, and be used more and more widely now. Because, the USB disk is more faster, reliable, and affordable than old floppy disk.

So, when we want to check one disk or drive of target system is removable or not, we may be thinking of using API function "GetDriveType()". Yes, it really works on some USB device, such as 16MB, <st1:place w:st="on"><st1:city w:st="on">32<st1:state w:st="on">MB, <st1:postalcode w:st="on">64<st1:state w:st="on">MB, and 128MB. ;-) Here, how about removable hard disk which is connected to system by USB channel? - Windows will report them as 'Fix Disk', and we would get the same result using 'GetDriveType()' function.

How can we differentiate between these USB ‘Fix Disk’ and Those IDE ‘Fix Disk’? Here is the solution for this event.


(Why do I want get the USB disks' drive letter properly? Because I want to check the virus while one new USB drive is inserted. We should not be remiss of the virus which is more and more technical day by day:)

Since we can get the base information about the disk type (using API Function ‘GetDriveType()’), we may only want to check the ‘Removable Hard Disk’ to verify its bus-type. Well, we’ll have two steps to get the USB disk’s drive letters:

Code Thoughts

1. Get the disks base information:

switch ( GetDriveType( szDrvName ) ) 
 case 0: // The drive type cannot be determined.
 case 1: // The root directory does not exist.
 drivetype = DRVUNKNOWN;
 case DRIVE_REMOVABLE: // The drive can be removed from the drive.
 drivetype = DRVREMOVE;
 case DRIVE_CDROM: // The drive is a CD-ROM drive.
 case DRIVE_FIXED: // The disk cannot be removed from the drive.
 drivetype = DRVFIXED;
 case DRIVE_REMOTE: // The drive is a remote (network) drive.
 drivetype = DRVREMOTE;
 case DRIVE_RAMDISK: // The drive is a RAM disk.
 drivetype = DRVRAM;

These codes above are based on ‘Article ID: Q161300 HOWTO: Determine the Type of Drive Using Win<st1:chmetcnv w:st="on" unitname="’" sourcevalue="32" hasspace="False" negative="False" numbertype="1" tcsc="0">32’ from MSDN.

2. Determinate the bus type of the ‘Fix Disk’:

Now, we may embed our codes at the ‘case = DRIVE_FIXED’:

Open the drive which we get now:

hDevice = CreateFile(szBuf, 

If we opened this drive, check its BUSTYPE, using API GetDisksProperty():

if(GetDisksProperty(hDevice, pDevDesc))
 if(pDevDesc->BusType == BusTypeUsb) // This is the ‘Check Point’!!! ;-)
  // We store the drive letter here
  szMoveDiskName[k] = chFirstDriveFromMask(temp); 

Close this drive when we finished our work on it:


3. How does the GetDisksProperty() work?

* FUNCTION: GetDisksProperty(HANDLE hDevice, 
* PURPOSE: get the info of specified device
BOOL GetDisksProperty(HANDLE hDevice, 
 STORAGE_PROPERTY_QUERY Query; // input param for query
 DWORD dwOutBytes; // IOCTL output length
 BOOL bResult; // IOCTL return val

 // specify the query type
 Query.PropertyId = StorageDeviceProperty;
 Query.QueryType = PropertyStandardQuery;

 bResult = ::DeviceIoControl(hDevice, // device handle
 IOCTL_STORAGE_QUERY_PROPERTY, // info of device property
  &Query, sizeof(STORAGE_PROPERTY_QUERY), // input data buffer
  pDevDesc, pDevDesc->Size, // output data buffer
  &dwOutBytes, // out's length

 return bResult;


  1. There are some structures not commented, see usbdisks_src for them.;
  2. Floppy drive (A: or B:) is reported as USB Disks by this demo, -And- it is easy to correct this, just putting some codes to the ‘case = DRIVE_REMOVABLE:‘;


  • 2004-03-29 - 1st GO


This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)


About the Author

Software Developer emware
China China
software development is so nice and we can make our world better than ever, even the real world.
vc++6 is enough for me, althought i tried to upgrade to higher version, each time, i down-grade to vc6. ^_^

Comments and Discussions

QuestionDownload Pin
AshutheGreat28-Oct-17 3:16
MemberAshutheGreat28-Oct-17 3:16 
QuestionHow to get source code??? Pin
Roman Myskovets'27-Jul-17 6:14
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Questionimplement Pin
Member 100390669-May-13 2:32
MemberMember 100390669-May-13 2:32 
Generalstruct alignment issue Pin
aandsc23-Nov-09 4:49
Memberaandsc23-Nov-09 4:49 
GeneralRe: struct alignment issue Pin
bachtkb2-Dec-09 16:03
Memberbachtkb2-Dec-09 16:03 
Generalquerying through IOCTL_STORAGE_QUERY_PROPERTY Pin
usb_uv21-Apr-09 20:53
Memberusb_uv21-Apr-09 20:53 
QuestionHow to Prepare a USB Drive for Safe Removal Pin
usb_uv17-Feb-09 22:28
Memberusb_uv17-Feb-09 22:28 
QuestionIs there a .NET version? Pin
Tony Reynolds26-Jan-09 4:44
MemberTony Reynolds26-Jan-09 4:44 
GeneralVery useful and clear article. Thanks a lot! Pin
Laurent Cozic17-Dec-08 11:28
MemberLaurent Cozic17-Dec-08 11:28 
GeneralCreateFile function returns -1 Pin
usb_uv20-Aug-08 10:49
Memberusb_uv20-Aug-08 10:49 
GeneralRe: CreateFile function returns -1 Pin
bachtkb2-Dec-09 16:10
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GeneralAvoid the Windows XP popup on inserting a USB device Pin
AlexEvans14-Jul-08 22:12
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GeneralPen Drive letter detection.. [modified] Pin
amshoyeb16-Mar-08 19:38
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GeneralSD card CID register Pin
mitya200515-Nov-07 3:27
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QuestionHow to get the vendor IDs & product IDs of all USB devices Pin
Vjys20-Feb-07 2:42
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GeneralError code 87 Pin
Volperossa20-Oct-06 6:01
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GeneralRe: Error code 87 Pin
Marcel_NL28-Mar-07 5:50
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GeneralRe: Error code 87 Pin
wardk29-Mar-07 3:26
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GeneralRe: Error code 87 Pin
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GeneralAdministrative privileges required Pin
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GeneralNeat! ... BUT Pin
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GeneralThe link : Pin
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Generalthanks Pin
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QuestionHow to detect card in USB multi-card reader? Pin
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