Screensaver
A screensaver is a computer program that is started automatically after a set period of inactivity of all input devices and display on the screen varies. The spectrum ranges from a black screen with simple color change to complex 3D screen savers, who have a high entertainment value in part, at the expense of computation time.
It is usually completed as soon as an input device data is received (eg by moving the mouse or presses a key on the keyboard).
- 3.1 DOS
- 3.2 Microsoft Windows
- 3.3 Mac OS X
- 3.4 X Window System
Purpose
The purpose of screen savers were originally is to prevent a constant lining up picture would burn into the tube screens of the 1980s and early 1990s during longer breaks. In more modern CRT monitors and flat panel displays, the risk of burn-in is no longer so screensavers are now used only for entertainment or for reasons of data protection. The screen saver prevents that the curious can see during the absence of a user, what is on the screen. The optional prompt for a password for the reactivation of the work surface when you exit the screen saver can also prevent unauthorized access.
The first, most commercially successful screensaver After Dark in 1989, the Flying Toasters module still enjoys special cult status.
Distributed Computing
Often programs for distributed computing offer a screen saver. Here provide users their unused computing capacity for scientific calculations. The screen saver informed here the user about the currently held calculations. In general, it can be disabled in order to provide more capacity for the actual calculation available.
One of the first projects that used the technique of distributed computing, was the SETI @ home project of the University of California, Berkeley.
Power consumption
Against the use of screen savers saith the power consumption caused by it. Firstly, both the processor (CPU) must as - with elaborate screen savers - to spend even graphics cards computation time while the computer may done nothing else. On the other hand, the monitor must continue. While this was back in the 1980s and 1990s no role, since CPUs when idle continued to run anyway and the on and off of CRT monitors took a relatively long, modern personal computer, all components can put in a power saving mode usually even on short non-use. Modern flat screens can also turn off the backlight after a short non-use and thus effectively save power.
Technology
DOS
Under DOS, there was no single format for screen savers, there were programs (*. COM or * EXE. ) Are available and load a memory- resident program (similar to a driver) that the screen saver starts after some time, to re- applied with an input. One drawback was the consumption of (then scarce ) main memory.
Microsoft Windows
Under the operating system Windows screen saver programs are usually on the file extension. Recognize scr.
These are executable files, so they may be renamed in. Exe. The " Configure" and "Test", which can be found when you click the scr files in the Windows Explorer context menu will be passed to the executable program by command line parameters.
The parameters can be different from system to system, so Screensavers need to respond to all possible spellings, such as lowercase or "- " instead of " /".
Mac OS X
In Mac OS X screen saver have the file extension. Savers. You are, depending on which users can access them in / System / Library / Screen Savers /, / Library / Screen Savers / and in the user directory under / Users / USERNAME / Library / Screen Savers /.
X Window System
Taking free Unix-like systems that use a graphical user interface, the X Window System, XScreenSaver is widespread. The Desktop Manager KDE and GNOME have their own screen saver ( kscreensaver or gnome -screensaver ).
Other screens as computer monitors
Meanwhile, screensavers are also common on mobile phones or PDAs. But here, they hardly serve to protect the screen, but only for the entertainment of users. Some phones screensavers are to save simple animated GIF files or a simple time display energy. Even DVD players often have a screen saver function after prolonged display of a static image.