Tip 124: Determining Available Disk Drives in Visual Basic

July 1, 1995

Abstract

The Drive List Box control in Microsoft® Visual Basic® reports the names of each drive connected to the computer system. This article explains another method you can use to determine which disk drives are available.

Retrieving Disk Drives

The Drive List Box control provided in Microsoft® Visual Basic® displays a list of all available disk drives attached to the computer system. You can, however, retrieve this same information without using a Drive List Box control in your application.

The Visual Basic CurDir$ function identifies your current drive and directory. The syntax for the CurDir$ function is:

X$ = CurDir$

or

CurDir$ = "C:\TEMP"

When the first statement above is executed, CurDir$ retrieves the current path into the X string variable. The second statement above tells CurDir$ to switch to the TEMP directory on drive C. If you attempt to change to a nonexistent drive or directory, the CurDir$ function will generate an error condition.

In the example program, you use a For-Next loop to cycle through all possible disk drives that may be installed in the computer system. Each time through the loop, you ask CurDir$ to change to a new, higher disk drive letter. When the function reports that it cannot switch to the specified drive, you know that you have found the last available disk drive.

Example Program

This program shows how to retrieve all valid disk drives without using a Drive List Box control.

1. Create a new project in Visual Basic. Form1 is created by default.
   
   
2. Add a Text Box control to Form1. Text1 is created by default.
   
   
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 = ""
       For X = Asc("C") To Asc("Z")
           On Error Resume Next
           c$ = CurDir$(Chr$(X) & ":\")
           
           If Err Then
               Err = 0     'no such drive
           Else
               Text1.Text = Text1.Text & " " & Chr$(X)
           End If
       Next X
   End Sub
   

Run the example program by pressing F5. Click the command button. The Text Box control shows which disk drives are installed in the computer system.