Programmatically Get and Set the State of the CapsLock and NumLock Keys

The VK_CAPITAL virtual key constant defines the Caps Lock key.
The VK_NUMLOCK constant defines the Num Lock key.

If you need to programmatically turn on or off the Caps Lock or Num Lock key, you can use the following procedure:

procedure ToggleNumLock;
var
   KeyState: TKeyboardState;
begin
   //note: Use VK_CAPITAL for Caps Lock

   GetKeyboardState(KeyState) ;

   //simulate key events (down + up)
   if (KeyState[VK_NUMLOCK] = 0) then
   begin
     Keybd_Event(VK_NUMLOCK, 1, KEYEVENTF_EXTENDEDKEY or 0, 0) ;
     Keybd_Event(VK_NUMLOCK, 1, KEYEVENTF_EXTENDEDKEY or KEYEVENTF_KEYUP, 0) ;
   end
   else
   begin
     Keybd_Event(VK_NUMLOCK, 0, KEYEVENTF_EXTENDEDKEY or 0, 0) ;
     Keybd_Event(VK_NUMLOCK, 0, KEYEVENTF_EXTENDEDKEY or KEYEVENTF_KEYUP, 0) ;
   end;
end;

Note: The keybd_event function synthesizes a keystroke. We call it two times to generate WM_KEYUP and WM_KEYDOWN messages.

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