HOWTO: Toggle the NUM LOCK, CAPS LOCK, and SCROLL LOCK Keys
Last reviewed: December 5, 1997
Article ID: Q177674
The information in this article applies to:
Microsoft Visual Basic Learning, Professional, and Enterprise Editions for Windows, version 5.0
Microsoft Visual Basic Standard, Professional, and Enterprise Editions, 32-bit only, for Windows, version 4.0
SUMMARY
This article demonstrates how to toggle the NUM LOCK, CAPS LOCK, AND SCROLL LOCK keys under both Windows 95 and Windows NT.
MORE INFORMATION
To toggle the NUM LOCK, CAPS LOCK, or SCROLL LOCK keys, you can use the following logic:
- Use the GetKeyboardState function to determine the state of the key.
- Determine which operating system is being used with the GetVersionEx API.
(Windows 95 and Windows NT require different methods for toggling these
keys.)
- Under Windows 95, use the SetKeyboardState API function to set the state
of the key. Under Windows NT, use the keybd_event function to simulate a
key press.
This example shows how to toggle these three keys to "on" if they are "off." This sample may be easily modified to toggle them off or just to check their state.
Sample Project
Start a new Standard EXE project in Visual Basic. Form1 is created by default.
Add a CommandButton to Form1.
Add the following code to the General Declarations section of Form1:
VB Code:
' Declare Type for API call:
Private Type OSVERSIONINFO
dwOSVersionInfoSize As Long
dwMajorVersion As Long
dwMinorVersion As Long
dwBuildNumber As Long
dwPlatformId As Long
szCSDVersion As String * 128 ' Maintenance string for PSS usage
End Type
' API declarations:
Private Declare Function GetVersionEx Lib "kernel32" _
Alias "GetVersionExA" _
(lpVersionInformation As OSVERSIONINFO) As Long
Private Declare Sub keybd_event Lib "user32" _
(ByVal bVk As Byte, _
ByVal bScan As Byte, _
ByVal dwFlags As Long, ByVal dwExtraInfo As Long)
Private Declare Function GetKeyboardState Lib "user32" _
(pbKeyState As Byte) As Long
Private Declare Function SetKeyboardState Lib "user32" _
(lppbKeyState As Byte) As Long
' Constant declarations:
Const VK_NUMLOCK = &H90
Const VK_SCROLL = &H91
Const VK_CAPITAL = &H14
Const KEYEVENTF_EXTENDEDKEY = &H1
Const KEYEVENTF_KEYUP = &H2
Const VER_PLATFORM_WIN32_NT = 2
Const VER_PLATFORM_WIN32_WINDOWS = 1
Add the following code to the Click event of the CommandButton:
VB Code:
Private Sub Command1_Click()
Dim o As OSVERSIONINFO
Dim NumLockState As Boolean
Dim ScrollLockState As Boolean
Dim CapsLockState As Boolean
o.dwOSVersionInfoSize = Len(o)
GetVersionEx o
Dim keys(0 To 255) As Byte
GetKeyboardState keys(0)
' NumLock handling:
NumLockState = keys(VK_NUMLOCK)
If NumLockState <> True Then 'Turn numlock on
If o.dwPlatformId = VER_PLATFORM_WIN32_WINDOWS Then '===== Win95
keys(VK_NUMLOCK) = 1
SetKeyboardState keys(0)
ElseIf o.dwPlatformId = VER_PLATFORM_WIN32_NT Then '===== WinNT
'Simulate Key Press
keybd_event VK_NUMLOCK, &H45, KEYEVENTF_EXTENDEDKEY Or 0, 0
'Simulate Key Release
keybd_event VK_NUMLOCK, &H45, KEYEVENTF_EXTENDEDKEY _
Or KEYEVENTF_KEYUP, 0
End If
End If
' CapsLock handling:
CapsLockState = keys(VK_CAPITAL)
If CapsLockState <> True Then 'Turn capslock on
If o.dwPlatformId = VER_PLATFORM_WIN32_WINDOWS Then '===== Win95
keys(VK_CAPITAL) = 1
SetKeyboardState keys(0)
ElseIf o.dwPlatformId = VER_PLATFORM_WIN32_NT Then '===== WinNT
'Simulate Key Press
keybd_event VK_CAPITAL, &H45, KEYEVENTF_EXTENDEDKEY Or 0, 0
'Simulate Key Release
keybd_event VK_CAPITAL, &H45, KEYEVENTF_EXTENDEDKEY _
Or KEYEVENTF_KEYUP, 0
End If
End If
' ScrollLock handling:
ScrollLockState = keys(VK_SCROLL)
If ScrollLockState <> True Then 'Turn Scroll lock on
If o.dwPlatformId = VER_PLATFORM_WIN32_WINDOWS Then '===== Win95
keys(VK_SCROLL) = 1
SetKeyboardState keys(0)
ElseIf o.dwPlatformId = VER_PLATFORM_WIN32_NT Then '===== WinNT
'Simulate Key Press
keybd_event VK_SCROLL, &H45, KEYEVENTF_EXTENDEDKEY Or 0, 0
'Simulate Key Release
keybd_event VK_SCROLL, &H45, KEYEVENTF_EXTENDEDKEY _
Or KEYEVENTF_KEYUP, 0
End If
End If
End Sub
Press the F5 key to run the program. Click the CommandButton. The state of the CAPS LOCK, the NUM LOCK, and the SCROLL LOCK keys should all be "on."
REFERENCES
For additional information, please see the following articles in the Microsoft Knowledge Base:
ARTICLE-ID: Q127190
TITLE : HOWTO: Toggle the NUM LOCK, CAPS LOCK, and SCROLL LOCK Keys
--------------------------------------------------------------------------------
Additional query words: numlock capslock scrolllock key state
Keywords : vb432 VB4WIN vb5all vb5howto
Version : WINDOWS:4.0,5.0
Platform : WINDOWS
Issue type : kbhowto
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