Smartphones are mobile phones with computer like capabilities. What's that? Aha! Yes, you've not only heard of them, you've probably seen them as well. Packed with Internet access, email capabilities, address books, and a whole lot more, cell phones have come a long way since their first debut. But be careful not to confuse these newest toys with sandbox devices. The two most popular software programs used to compress and decompress files are Winzip and StuffIt respectively. There are other programs that do the same thing and there are even programs that can compress and decompress files for both the Windows and the Mac system. However since Winzip and StuffIt are the most popular, we will assume you will use either one to compress and decompress your own files. If you can remember that there are hoards of alternatives to costly commercial software (and you make the effort to get it), you'll discover that you can keep up with the rest of the computer industry at a significantly cheaper cost than if you attempted to pay your way down the software aisle. Software piracy just isn't the answer. But when one command conflicts with another command - or when one command asks for a process or information that isn't available, the computer returns results that aren't useable. That's an error. A prime example of this kind of error is when users attempt to use software that isn't applicable for their system. Understanding Operating Systems Every new computer that's brought home from the store has an operating system installed onto it. But what most new computer users don't realize, is that without an operating system, that computer would be a simple shell of possibilities. A powered computer lacking an operating system wouldn't display anything more than a bunch of confusing text messages that describe the computer's boot process. scr - This extension indicates a screen saver file. .sit - This extension indicates a Macintosh archive StuffIt file. They will not open on a Windows system without a special utility. .ttf - This extension indicates a font especially designed for use on a Windows system. It stands for "True Type Font.