Tip 165: Locating CD-ROM Drives Installed on a Computer System

December 5, 1995

Abstract

In a Microsoft® Visual Basic® application, you may need to determine what types of disk drives are installed on a computer system. This article explains how to locate the CD-ROM drives that are installed.

Using the GetDriveType Function

Occasionally, in a Microsoft® Visual Basic® application you may need to determine whether a specific disk drive is a CD-ROM, removable, fixed, RAM, or network drive. You can easily make this distinction by using the Microsoft Windows® application programming interface (API) GetDriveType function.

The following Declare statement should be included in your project:

Private Declare Function GetDriveType Lib "kernel32" Alias "GetDriveTypeA" 
   (ByVal nDrive As String) As Long

To use the GetDriveType function, you need to tell it the name of the disk's root directory. This should be in the format "c:\". After you call it, the GetDriveType function returns a value that indicates the type of disk drive.

The value returned by the GetDriveType function may be one of the following:

As you know, all disk drives are identified by an alphabetic letter, starting with the letter A. The ASCII value for the letter A is 65. Because there are 26 possible disk drives, you can use a For-Next loop to test each possible disk drive to determine whether it is a CD-ROM disk drive.

Example Program

This program shows how to locate all CD-ROM disk drives installed on the computer system.

1. Create a new project in Visual Basic. Form1 is created by default.
   
   
2. Add the following Declare statement to the General Declarations section of Form1 (note that the Declare statement must be typed as a single line of code):

   Private Declare Function GetDriveType Lib "kernel32" Alias "GetDriveTypeA" 
      (ByVal nDrive As String) As Long
   

3. Add a Command Button control to Form1. Command1 is created by default.
   
   
4. Add the following code to the Click event for Command1:

   Private Sub Command1_Click()
       Text1.Text = FindCDROM
   End Sub
   

5. Add a Text Box control to form1. Text1 is created by default. Set its MultiLine property to True.
   
   
6. Create a new function called FindCDROM. Add the following code to this function:

   Function FindCDROM() As String
       Dim Drive As Integer
       Const DRIVE_CDROM = 5
       FindCDROM = "No CD_ROM Installed"
   
       For Drive = 65 To 90
           If GetDriveType(Chr(Drive) & ":\") = DRIVE_CDROM Then
               FindCDROM = "CD-ROM Drive " & Chr(Drive) & ":\"
               Exit For
           End If
       Next Drive
   End Function
   

Run the example program by pressing F5. Click the Command Button control. A list of all CD-ROM disk drives installed on the computer system appears in the Text Box control.