A screensaver is a computer program that blanks the screen or fills it with moving images or patterns when the computer has been idle for a long time. The original purpose of screensavers was to prevent phosphor burn-in on CRT and plasma computer monitors. Though modern monitors are not susceptible to this issue, screensavers are still used for other purposes. Screensavers are often set up to offer a basic layer of security, by requiring a password to re-access the device. Some screensavers use the otherwise unused computer resources to do useful work, such as processing for distributed computing projects.
