Screensaver Purpose

Screensaver programs were designed to help avoid effects by automatically changing the images on the screen during periods of user inactivity.

Older machines designed without burn-in problems taken into consideration often display evidence of screen damage, with images or text such as "Please insert your card" (in the case of ATMs) visible even when the display changes while the machine is in use. Blanking the screen is out of the question as the machine would appear to be out of service. In these applications, burn-in is prevented by shifting the position of the display contents every few seconds, or by having a number of different images that are changed regularly.

Modern CRTs are much less susceptible to burn-in than older models due to improvements in phosphor coatings, and because modern computer images are generally lower contrast than the stark green- or white-on-black text and graphics of earlier machines. LCD computer monitors, including the display panels used in laptop computers, are not susceptible to burn-in because the image is not directly produced by phosphors. For these reasons,screensavers today are primarily decorative or for entertainment, and usually feature moving images or patterns and sometimes sound effects.

One increasingly popular application is for screensavers to activate a useful background task, such as a virus scan or a distributed computing application. This is convenient because these things only use resources when the computer would be otherwise idle, and thus are very efficient.