Microsoft KB Archive/63608

TSR Utility for Disabling CTRL+ALT+DEL Keystroke Combination PSS ID Number: Q63608 Article last modified on 09-24-1993 PSS database name: O_MSDOS

4.00

MS-DOS

= SUMMARY =

This article explains how to obtain a terminate-and-stay-resident (TSR) program that disables the CTRL+ALT+DEL keystroke combination.

= MORE INFORMATION =

The process responsible for recognizing the CTRL+ALT+DEL keystroke combination and initiating a system reboot (warm boot) is in the ROM BIOS keyboard hardware interrupt 9 service routine. To prevent the ROM BIOS INT 9 ISR from acting on this keystroke combination, a new replacement interrupt 9 service routine must be installed in the form of a TSR program. The new INT 9 ISR will detect and eliminate the CTRL+ALT+DEL keystroke combination altogether from the system but will still allow other keystrokes or combinations of keystrokes to pass through unchanged to the original ROM BIOS INT 9 ISR.

A sample replacement INT 9 ISR that disables the CTRL+ALT+DEL keystroke combination is included in the file NOCAD, which can be found in the Software/Data Library by searching on the word NOCAD, the Q number of this article, or S12621. NOCAD was archived using the PKware file-compression utility.

The archived version of NOCAD contains the source code and the executable version of NO_CAD!.

NO_CAD!.COM is a TSR program that can be installed in your system by including it in your AUTOEXEC.BAT file, or by invoking it from the MS-DOS command line. Once NO_CAD!.COM is installed, the only way to manually reboot your system is to use the reset switch or main power switch on your computer.

Additional reference words: 4.00 noupd softlib

Copyright Microsoft Corporation 1993.