How to Find Next Available Drive Letter (for Network Connect)

• Professional and Enterprise Editions of Microsoft Visual Basic, 16-bit and 32-bit, for Windows, version 4.0

SUMMARY

The Visual Basic program in this article shows by example how to find the next available (unused) drive letter in Windows. This is useful when making network connections to a new drive letter.

MORE INFORMATION

Step-by-Step Example

The Freedrive function defined below returns the next drive letter available in Windows, followed by a colon (:).

1. Start Visual Basic. Form1 is created by default.

2. Add the following code to the General Declarations section of Form1:

  Private Declare Function GetDriveType Lib "kernel32" Alias

  Private Declare Function GetDriveType Lib "kernel" (ByVal nDrive As

Function Freedrive()

      Dim DriveNum As Integer, FirstFreeDrive As String
      Dim FirstDrive As Integer
      DriveNum = -1
      Do
         DriveNum = DriveNum + 1   ' start at drive zero.
         #If Win32 Then
           NextDrive$ = Chr$(DriveNum + 65) + ":\"
           FirstDrive% = GetDriveType(NextDrive$)
         #Else
           FirstDrive% = GetDriveType(DriveNum)
         #End If
         ' GetDriveType returns zero if it cannot determine drive
         ' type or returns 1 if the specified drive does not exist.
      #If Win32 Then
        Loop Until FirstDrive% = 1
      #Else
        Loop Until FirstDrive% = 0
      #End If
      ' DriveNum of 0 means Drive A, 1=B, 2=C, 3=D, 4=E, 5=F, and so on:
      FirstFreeDrive = Chr$(DriveNum + 65) + ":"
      Freedrive = FirstFreeDrive

1. In the Form_click event, add the following statements:

      Private Sub Form_Click ()
   
         Cls
         Print "The next available (unused) drive letter is: "; Freedrive()
   
         ' More handy tips: The "App" object below is found in VB 2.0
         ' and 3.0 (but not 1.0).
         Print "The title for the EXE in Windows Task Manager: "; app.Title
         Print "The name of this EXE, or project in VB, is: "; app.EXEName
         Print "The path to this application is: "; app.Path
   
      End Sub
   
   

2. Run the program, and click the form.