An example of an error in this part of an interface would be if an option was missing or grayed out (lighter in color). Tool bar - this part of a program displays small icons across the top which represent tools. Clicking an icon will open a tool or process a command that might also exist on a program's menu bar. That's why software programs include minimum memory requirements. A program that needs 14MB of memory will generate errors on a computer that only has 4MB of memory if it runs at all. The same goes for disk space, monitor color depth and resolution. In these situations, problems occur the moment that a piece of software attempts to access the things (hardware, memory, space, resolution, etc. There are hoards of advanced contact database programs floating around the Internet and on store shelves, but Windows provides a completely competent contact database of its own simply known as "Address Book." This small compact utility allows users to organize contacts by name, location, group, or number and it give users ample space to fully describe each. But we can still introduce you to some of programming's most basic concepts - starting with the commands we talked about earlier. Commands are the instructions that a computer follows to perform an action. 2 To make them work inside of a program, programmers assign commands to objects like buttons for example. txt - This extension indicates a plain text file that can be opened with Notepad. .wav - This extension indicates a sound file that like the .mp3 file, can be opened with Windows Media Player or Windows Sound Recorder. .Wav files are much larger than .mp3 files. .zip - This extension indicates a Windows archive WinZip file. Although Window's defrag system can ease some of the stress that these files place onto the drive, it doesn't do much to get rid of the problem in the first place. This is because the defrag program simply organizes the files in a system that makes it easier for the computer to access. (Thus cutting down on the work required to find and load them).