Programming a computer is creating a sequence of instructions that enable the computer to do something.1 The people who program computers (called programmers) use a programming language to communicate with a computer. You might have heard of some of these languages in the past such as Visual Basic, C++, or Fortran. 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. Although those better-known brands may be a tad bit more expensive, the computer novice will appreciate the comfort in purchasing a computer from a business that has a long record of building quality products, and that has the funds available for fulfilling returns, trades, servicing, and warranties. Since we're describing a home network that will connect to the Internet, you're strongly advised to install a protective firewall program to thwart Internet viruses, worms, or other damaging spyware code. Firewalls prevent - but they don't repair. Only anti-virus and anti-spyware programs can reverse damage. It keeps track of where things exist on a computer's hard drive as well. But perhaps most importantly for the end-user, the operating system is responsible for translating commands issued with a keyboard and mouse into binary code (010110101 stuff) that can communicate with a set of speakers, a printer, a scanner, and more. gif - This extension indicates another image file and it stands for "Graphics Interchange Format." .Gif files are often smaller than .bmp files (described earlier) and they're commonly found on Internet web pages. .jpg - This extension indicates yet another image file and it stands for "Joint Photographers Experts Group.