Viruses that destroy data are known as Trojan horses, viruses that explode their attacks are called bombs, and viruses that duplicate themselves are called worms. Some viruses are a combination of each, however they can be further identified according to where they're located on a computer. A virus originating from the boot sector of a computer is a boot-sector virus and this nasty devil does its dirty work the moment a computer is turned on. 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." .txt - This extension indicates a plain text file that can be opened with Notepad. .wav - This extension indicates a sound file that like the . Or if a program were to calculate a date "x" days from now, the variable "x" would be an unknown piece of data until we tell the program what "x" is. In programming, it's sometimes required to work with unknown pieces of data. That's when conditions come in handy. 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. Connecting computers with either an Ethernet cable or a Wireless connection can create a home network. The easiest and cheapest method uses an Ethernet connection, which requires a series of network cards, a cable for each computer, and a router. The network card is similar to the old modems we used in the past to connect to the Internet, however in a home network, it's used to communicate with every computer that's connected to it. Basic GUI Terminology Knowing What You're Working With Helps Technicians Getting help with your computer software can be easier when you know the correct terms to use. One of the biggest problems that new computer users have with technical support is not knowing how to correctly describe the problem that they're having. You can reach these systems by calling the phone number associated with the product that you're having trouble with. Calls may be free (1-800 or 1-877 number), or they may cost a small fee (1-900). 6. PC support groups or user groups are another option for help. These are groups that meet in libraries, computer stores, or other local areas and they discuss all sorts of issues related with a particular product.