Turning the SCROLL LOCK Key On

MS-DOS                 | WINDOWS

The information in this article applies to:

• Microsoft C for MS-DOS, versions 6.0, 6.0a, and 6.0ax
• Microsoft C/C++ for MS-DOS, version 7.0
• Microsoft Visual C++ for Windows, versions 1.0 and 1.5

SUMMARY

The following code illustrates how to turn the SCROLL LOCK key on in your program. Note: This code is only for use with MS-DOS. Running it with OS/2 will cause a protection violation. Use the OS/2 FAPI function KbdSetStatus() to set the status of shift flags when writing programs that will run with OS/2 or be bound to run with both MS-DOS and OS/2. This technique will cause a general protection violation if attempted in a Windows or QuickWin application. The Windows SDK has functions GetKeyboardState() and SetKeyboardState() for checking and setting the lock keys on the keyboard.

MORE INFORMATION

Sample Code

/* Compile options needed: none
*/

#include <stdio.h>

   /* Get the address of the keyboard status byte */
   char far *kbdstat = (char far *) 0x00000417;

   char scrollmask = 0x10;

   /* OR *kbdstat with scrollmask to set bit 4 in the
      keyboard status byte to 1 */

   *kbdstat = *kbdstat | scrollmask;

Additional information on keyboard status can be found in the Peter Norton "Programmer's Guide to the IBM PC and PS/2."