Application programs are at the top of your computer's logical structure, and for most people, they are the whole point of using a computer. Applications are the programs you use to read and write letters, term papers and books, crunch numbers, listen to music, view Web pages through the Internet and movies from DVDs, create pictures, play games, and do everything else a computer does. As you know, there are thousands of application programs out there, each of which provides a unique combination of features and functions.
Applications relate to the operating system (which is the next layer down) through the Application Program Interface discussed earlier in this chapter. The command interpreter in an application converts the instructions you supply to the program into standard API commands.