Why there are screen savers in a PC?

I want to know the need of screen saver in a pc. As I know from somewhere, it is to prevent the effieciency of processor from going down while power is on and we are not working. But, I am somewhat confused about is it for efficiency of processor or Monitor. If the screensavers are for Monitor then how they effects?

When computers used cathode-ray picture tubes before lcd screens, a constant image like the desktop image would burn a ghostly image on the phosphors of the screen. This would make the phosphors of the monitor screen not glow as efficiently or brightly. This problem doesn't exist with today's lcd monitors. Screensavers would be used to prevent the burning because they are animated and the image of the screensaver constantly changes and because of that, there is no chance for a screensaver to burn an image on the monitor screen.

screensavers entertain the user while he is not using the pc.

I think it saves power.

they are ther to prevent burnin in monitors

it's not for that, who the hell told you that. lol

monitors, if left with one picture, sometimes have that image burnt into the screen if left for a long time with it on there. and you will always have a ghostly image of that there. so the screen saver is ther to 'save' the screen from that damage.

but i dont really think it matters with the newer screens. so there really there now for the look.

If an image is displayed on a monitor for an extended period of time, it will 'burn' the image into the monitor. What that means is that there will be a faint outline/colorization that will permanently display on the screen. Screen savers are animated to keep one static image from being displayed for extended periods of time.

In CRT (older tube style monitors), the image being projected on the screen over a long period of time will eventually burn its patten on the inside of the glass. Once it is burned in there it will appear all of the time no matter what the computer is sending to the monitor. You can see this in the older ATM machines and in many UNIX servers that are left on with the menu displayed for hours at a time.

The screen saver, with constant motion will "save the screen" from burining images into the phosphors and eliminate the need for replacement or having to deal with constant background (or foreground as the case may be) ghost images of the default screen.

originally used to keep the image from literally permanently burned into the monitor. now it is mostly entertainment and some security if you set it to request your password.