Screen saver
A screen saver , also known as a screensaver , is a computer program that starts automatically after all input devices have been inactive for an adjustable period and varies the display on the screen . The spectrum ranges from a black screen and simple color changes to complex 3D screen savers , some of which are highly entertaining, but at the expense of computing time .
It is usually terminated as soon as data is received via an input device (e.g. by moving the mouse or pressing a key on the keyboard ).
purpose
The purpose of screen savers was originally to prevent a constant image from being burned into the CRT screens of the 1980s and early 1990s during long breaks . With more modern tube monitors as well as LCD and plasma screens , there is no longer the risk of burn-in, so that screen savers are only used here for entertainment or for reasons of data protection . However, screensavers could become relevant again with the advent of OLED displays , whose luminosity decreases after many hours of operation, but this is weakened by the fact that almost all modern screens have energy-saving modes, which means that the screen can also be simply switched off. Certain screen savers prevent unauthorized persons from seeing what is on the screen while a user is away. The optional request to enter a password for reactivating the work surface when closing the screen saver can also prevent unauthorized access.
The first screen saver that was commercially successful worldwide was After Dark in 1989 , the Flying Toasters module of which still enjoys cult status today.
Distributed computing
Programs for distributed computing often also offer a screen saver. Here users make their unused computing capacity available for scientific calculations. The screen saver informs the user about the current calculations. As a rule, it can be deactivated in order to provide more capacity for the actual calculation.
One of the first projects to use distributed computing was the SETI @ home project at the University of California, Berkeley.
Power consumption
The power consumption they cause speaks against the use of screen savers. On the one hand, both the processor (CPU) and - with complex screen savers - graphics cards have to use computing time, while the computer may not do anything else. On the other hand, the monitor must also continue to run. While this did not play a role in the 1980s and 1990s, since CPUs continued to run when inactive and it took a relatively long time to switch CRT monitors on and off, modern personal computers can usually switch all components to an energy-saving mode even if they are not used for a short period of time . Modern flat screens can also switch off the background lighting after a short period of inactivity, effectively saving electricity.
technology
DOS
Under DOS there was no uniform format for screen savers, there were programs ( * .COM or * .EXE ) available that a memory-resident load program (similar to a driver) that starts the screen saver after some time, to again held an input. A disadvantage was the consumption of (then scarce) main memory. With some programs such as Norton Commander you could start the program's own screen saver by moving the "mouse pointer" to the upper right corner (also known as the "sleeping corner"). With Norton Desktop for Windows 3.11, the "sleeping corner" and another corner "Never fall asleep" could be selected in the settings.
Microsoft Windows
| parameter | meaning |
|---|---|
| / S | starts the screen saver in full screen mode . |
| / C | opens the internal configuration menu. |
| / P X | runs the program in preview mode, X is a second parameter that represents the handle to a window area in which the preview is to be shown. |
Under the Windows operating system , screen saver programs can usually be recognized by their file extensions .scr .
These are executable files , so they can be .exerenamed to. The "Configure" and "Test" functions, which can be found in the context menu when you click the scrfiles in Windows Explorer , are transferred to the executable program using command line parameters.
The parameters can differ from system to system, so screen savers must react to all possible spellings, such as: B. lowercase letters or "-" instead of "/".
Mac OS X
In Mac OS X , screen savers have the file extension .savers or .qtz. You are, depending on which users can access them under /System/Library/Screen Savers/, /Library/Screen Savers/and in the user directory under .
/Users/BENUTZERNAME/Library/Screen Savers/
X Window System
Under free Unix-like systems, the graphical interface, the X Window System use is XScreenSaver common. The desktop managers KDE and GNOME have their own screen savers ( kscreensaver and gnome-screensaver ).
Screens other than computer monitors
In the meantime, screen savers are also often found on cell phones and PDAs . Here, however, they hardly serve to protect the displays, but only to entertain the user. On some phones, screensavers are simple animated GIF files or a simple time display to save energy. Even DVD players often have a screen saver function after prolonged display of a still image.
Web links
Individual evidence
- ↑ scc.kit.edu (PDF)