Security

Screensaver software can to some extent perform  a security function.  For example, a lot of screensavers  have the option of asking  a user for a password  to permit him to start  working. However, there is a way to enter just by restarting the computer. But it works if the owner of computer set an option to log in automatically  upon start-up. 

Microsoft Windows

The older Windows version used to have the problem of installing a virus. Any opened file which had ".scr"  suffix  was automatically executed by Windows. Thus, any virus or malware was able to install itself. In the modern versions of Windows there is an option of  reading the tags left by an application and verifying the publisher of the file. 

History

Today modern graphics technologies allow to create  a wide  choice of different screensavers. With 3D  computer graphics it has become possible to create 3D screensavers which look natural.

The inventor of the first screensaver was John Socha who is also known for creation of the Norton Commander. Besides, it was he who invented the term screen saver. In the year 1983 in December  issue of Softalk magazine the screensaver named scrnsave was published.  If the screen  was inactive for 3 minutes, it  blanked ( this interval  could not be changed).Soon on Apple's Lisa appeared the screensaver enabling the users to change the interval of activation.

The history of screen savers dates back to  Atari VCS/2600 gaming console which  included color cycling. In  1979  the Atari 400 and 800 appeared.  If they were left inactive the  color changes occurred. These are the examples of the earliest screensavers in ROM .

Underlying architecture

In order to create a screensaver a great variety of programming languages and graphic interfaces is used. The most typically used are C or C++ programming languages,   Graphics Device Interface (GDI), DirectX. To create some Mac OS X screensavers Quartz Extreme graphics layer is used. A screensaver usually shuts down when there is a message that the mouse was moved or a key pressed.