Microsoft KB Archive/127190

{|
 * width="100%"|

HOWTO: Toggle the NUM LOCK, CAPS LOCK, and SCROLL LOCK Keys

 * }

Q127190

-

The information in this article applies to:


 * Microsoft Win32 Software Development Kit (SDK)

-

SUMMARY
The documentation for SetKeyboardState correctly says that you cannot use this API to toggle the NUM LOCK, CAPS LOCK, and SCROLL LOCK keys.

You can use keybd_event to toggle the NUM LOCK, CAPS LOCK, and SCROLL LOCK keys under Windows NT. The same technique works for toggling CAPS LOCK and SCROLL LOCK under Windows 95, but it will not work for NUM LOCK.

MORE INFORMATION
The following sample program turns the NUM LOCK light on if it is off. The SetNumLock function defined here simulates pressing the NUM LOCK key, using keybd_event with a virtual key of VK_NUMLOCK. It takes a boolean value that indicates whether the light should be turned off (FALSE) or on (TRUE).

The same technique can be used for the CAPS LOCK key (VK_CAPITAL) and the SCROLL LOCK key (VK_SCROLL).

Sample Code
  /* Compile options needed: */

#include 

void SetNumLock( BOOL bState ) {     BYTE keyState[256];

GetKeyboardState((LPBYTE)&keyState); if( (bState && !(keyState[VK_NUMLOCK] & 1)) ||         (!bState && (keyState[VK_NUMLOCK] & 1)) ) {     // Simulate a key press keybd_event( VK_NUMLOCK,                     0x45,                      KEYEVENTF_EXTENDEDKEY | 0,                      0 );

// Simulate a key release keybd_event( VK_NUMLOCK,                     0x45,                      KEYEVENTF_EXTENDEDKEY | KEYEVENTF_KEYUP,                      0); }  }

void main {     SetNumLock( TRUE ); } Additional query words:

Keywords : _IK kbInput kbKeyIn kbOSWinNT kbOSWin2000 kbSDKWin32 kbGrpDSUser kbOSWin

Issue type : kbhowto

Technology : kbWin32SDKSearch kbAudDeveloper kbSDKSearch kbWin32sSearch