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Posted 25 Jul 2008


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Turn off laptop monitor and lock the system

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2.33/5 (5 votes)
25 Jul 2008CPOL1 min read
simple code to replace the win+L hotkey


I use the Thinkpad laptop for my research work. Usually, I keep it working in the night for the simulation work. Therefore, when I wake up at the next morning, I can analyze the results immediately. I need to lock the WinXP system and turn off the monitor when I leave the laptop. Then I write this program to help me. It is more convenient to use than the traditional way (Win+L hotkey to lock the system and turn off monitor through power schemes).

Code explanation

The code is very simple.

First, turn off the monitor by using SendMessage function. You can find more introduction about it from this article.

// Turn off monitor
Sleep(500); // Eliminate user's interaction for 500 ms

Second, use LockWorkStation function to lock the system.


Third, the LockWorkStation function requires Windows Vista, Windows XP, or Windows 2000 Professional. To compile the program successfully, we need to add the following macro in the StdAfx.h.

#define _WIN32_WINNT 0x0500
This program is very simple yet very useful. It keeps your task running on the laptop while turns off the monitor for saving energy and protects the laptop from unauthorized use.



This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Written By
Beihang University
China China

Comments and Discussions

Praisethank you very much Pin
Member 1564270419-May-22 7:16
Member 1564270419-May-22 7:16 
xiexie dashen, NB 666
GeneralRemove intermediate files from source archive Pin
aroth8227-Jul-08 20:14
aroth8227-Jul-08 20:14 
GeneralYou shouldn't broadcast the monitor power message. [modified] Pin
Leo Davidson26-Jul-08 22:42
Leo Davidson26-Jul-08 22:42 

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