Those Magnificent Screen Savers

by Philip J. Erdelsky
Home page: http://www.alumni.caltech.edu/~pje
E-mail: pje@acm.org

This article first appeared in ComputorEdge on October 29, 1993, and is reproduced here by permission.

All across the land, computer users are doing double takes as they catch sight of their coworkers' computer screens. Small crowds are gathering around computers and chuckling. Still others are staring intently at their computers, oblivious to everything else.

What's going on here? Some new killer application?

No, what's attracting all this attention is one of the smallest and seemingly most insignificant computer applications, the screen saver.

What's a screen saver? And what does it save?

On television screens and early computer screens, images that stayed fixed for long periods of time used to burn themselves permanently into the screen and reappear as ghostly images when anything else was displayed. That was never a problem with television (unless somebody left a test pattern on), but it was a problem with video games and even more of a problem with computer applications, which usually change their displays only in response to operator actions. More than one old video terminal showed the faint image of a system prompt in the upper left corner.

The solution was an automatic screen saver. If there was no input from the keyboard, joystick, trackball or mouse for more than a minute or two, the computer would erase the screen but save the image. Any subsequent input would instantly restore the image.

However, the first screen savers had one shortcoming. There was no way to tell by looking at the screen whether the computer was still running. So the next generation of screen savers didn't just erase the screen. They displayed some moving or changing image that wouldn't burn itself into the screen but would allow the user to see at a glance that the computer was still running.

Modern computer screens aren't as vulnerable to burn-in as the old ones, but screen savers seem to have taken on a life of their own. Some of the most imaginative and creative computer graphic designs have appeared as screen savers. Screen savers are now an integral part of Microsoft's Windows and some other graphical user interfaces as well.

Like a limerick in poetry, a computer-generated image has to meet certain conditions to qualify as a screen saver:

  1. A screen saver has to change in such a way that every part of the screen goes blank from time to time. That is required to prevent burn-in, at least in theory.
  2. A screen saver has to change fast enough to show that the computer is running.
  3. A screen saver has to fit onto a standard computer screen.
  4. A genuine screen saver has to be simple enough so it can run without disk swapping, once it gets going.

That still leaves a lot of room for cleverness and innovation. And it doesn't take a large company with lots of resources to write a screen saver -- it just takes one programmer with a clever idea. As a result, there are lots of screen savers, and many of them are available as shareware or freeware.

Some screen savers also serve another purpose. After they erase the screen, you have to supply a password to restore the image. This feature is quite useful if you're working on something confidential, but it's not part of the art.

Most screen savers, like most works of art, are rather prosaic. There are many screen savers that feature company logos or other commonplace objects floating, flying, bouncing or crawling across the screen.

Some screen savers are rather elaborate. At least one looks like a well-stocked aquarium.

Some screen savers are quite funny. For example, there is one showing a person mowing a lawn. By the time the mower gets to the bottom of the screen, the grass at the top of the screen has grown back. The humor may grow a little stale with repetition, but it's always entertaining to everyone when a visitor sees it for the first time. This kind of screen saver makes a great conversation piece.

Some screen savers are quite hypnotic. There is one in Windows called "Mystify", which is probably not the world's best aid to hypnosis, but it's fairly effective anyway. It's rather hard to describe in print, but here's an attempt. Think of eight little balls bouncing around the screen. Then connect the balls with lines to form two quadrilaterals. Make the balls invisible, and watch the quadrilaterals as they bounce around, changing shape and changing color. You are getting very sleepy...

Some screen savers retain part of the original image so you can see what you were working on. There's one that looks like someone is holding a board with a circular knothole in front of the screen. The hole bounces around, revealing glimpses of the original image as it passes. Another one slices the screen up into squares, blanks out a few squares, and then slides the squares around like an old game that used squares numbered from 1 to 15. This one qualifies as a screen saver only because the blanked-out squares travel around to all parts of the screen.

All of the new graphics techniques are finding applications in screensavers. There are a number of fractal screen savers. Bouncing, flying and falling are common techniques.

Still undecided is whether the Newton's laws of motion are the most effective for screen savers. To prevent repetition, many screen savers that use bouncing don't always keep the angles of incidence and reflection equal. Maybe a relativistic screen saver would be more artistic. Or perhaps something that neither Newton, nor Einstein, nor any other physicist has thought of because it would be impossible in the real world.

Erotic art, the electronic equivalent of "girlie" calendars, is sure to show up in screen savers, if it hasn't already.

Finally, some screen savers are just plain weird. It's no surprise that many of the "Weird Software" awards from ComputorEdge are going to screen savers.

What we're seeing is the birth of a new art form. We can expect better, funnier, and more creative screen savers, some of which are bound to become classics of the genre. And unlike classic paintings, photographs, sculptures and films, they won't fade, chip or peel with age. They'll just be ported to newer computers.