Conditions allow a program to perform an action based on the outcome of a previous command.3 Using this type of instruction, we could instruct a program to do one thing if the "x" variable in our latter example turned out to be 7 days, and then do different thing if the variable turned out to be 3 days. If you use an online service like AOL (America Online), you can use its internal Parental Control settings to block access to various chatrooms and websites. You could even block instant messaging and email from anyone who isn't a fellow AOL user. Other tools available online operate similar to the way that AOL's Parental Control settings work, however no collection of tools could replace the reinforcement of mom and dad. Connected to the network, each computer can send files back and forth, open programs on a remote computer, play the sound files and videos located on another computer, and share a single Internet account to browse the web, download files, or chat with someone in an entirely different country. If a single printer is available on only one computer in the network, every connected PC can send documents to it and print them out. This is of course, assuming the kids are too young to whine about not having enough SDRAM or less than a 160GB hard drive. Today's "older" computers are perfectly capable of accommodating the needs of young PC users, and they're excellent machines for playing educational CDs, small multimedia files, or games downloaded from the Internet. Today it's really not safe to open files from anyone (without scanning the files) because that's how viruses get spread - through files - even by mistake. So even though your co-worker may have emailed a funny video, it's no more safe to open than a video downloaded from a complete stranger. Be safe and scan each and every file you download from the Internet or receive through email regardless of where it came from. Program B uses a file that Program A installed much earlier, but when Program B is run, errors popup. Those errors are the result of Program B attempting to use an outdated (shared) file that was installed by Program A. In order to fix that problem, the user would have to download an updated version of the shared file (which to say the least - is not an easy thing to find or do).