1. In general, close is the action performed to terminate a portion of a program or the complete it. If a file has changed since it was opened, and the program is closed, any changes to that open file may be lost. If the program closes without performing the close action, this is usually referred to as a crash.
2. When referring to a button or a feature in a GUI operating system, the close box or close button allows a user to terminate a window from a program or the complete program. For example, in most other operating systems and software programs, the close button (denoted with an "X") is located in the top right corner of the window. If there are multiple windows opened within the program, the "X" at the top right corner closes the program and all associated windows. If the "X" is within the program, it closes the corresponding window.
On an Apple Mac OS operating system, the close button is represented as a red button in the top right-hand corner of the window. The picture to the right shows the red, yellow, and green circles.
3. Close is also a command used to exit a program. For example, in an FTP session close can be used to exit the session. See the how to use FTP help page for information about close and other FTP commands.
4. Close is also the name of a physical action. For example, when a CD-ROM tray is ejected if you push in on the tray you are closing the tray.
5. When creating or writing to a CD-R disc your program or operating system may ask you if you want to "Close the disc." In this context, close refers to the disc being finalized so no additional information may be written to it. With some CD drives and players (especially early models) if the disc is not closed it cannot be read.