Close may refer to any of the following:
1. In general, close is the action performed to terminate a program or exit a file. If a file has changed since it was opened, and the program is closed, any changes to that open file may be lost unless they are saved before closing. If the program closes without performing the close action, this is usually referred to as a crash.
Tip: Press the keyboard shortcut key combination Alt+F4 in Windows to close a program or an Internet browser along with all of its tabs. If the program has any open windows, files, or tabs, press Ctrl+F4 or Ctrl+W to close them one at a time and keep the program open.
How to close Windows or another operating system
If you're done using your computer, you can shut down the computer to close everything and have the computer turn off.
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 operating systems and software programs, the close button (denoted by an "X") is located in the top-right corner of the window.
Example of a close button
If there are multiple windows opened within a program, the "X" at the top-right corner closes the program and all associated documents and files. Clicking any "X" below the top-right corner "X" will close the file or document in the program but not close the program. For example, in the example picture below of a window, you can see the close button in a red box with another X below the toolbar and on the Document1 tab. Clicking either of these would close Document1 but leave the TextPad program open.
Close button for Apple computer users
On an Apple macOS operating system, the close button is represented as a red button in the top-left corner of the window. The picture to the right shows the red, yellow, and green circles.
What if the close button is missing?
The close button may be hidden if the program is running in fullscreen or is a program that has decided to hide the close button (e.g., Windows 8 programs). Try moving the mouse to the top of the screen to see if the hidden close button reappears. If this does not work, try pressing the Esc key. If none of these suggestions work and you are running Windows, you can also use the keyboard shortcut Alt+F4 to close any Windows program.
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 the disc. With some early CD drives and players, if the disc is not closed, it cannot be read.