File Extensions


 by Allan J. Greenberg

The file extension is the alpha-numeric character or characters to the right of the dot (or period) in the file name. All file names end with the file extension. The extension indicates the format that the file is written in. When a file is saved, the computer operator provides the file name and the program used provides the file extension, unless the user chooses another file extension.

By default, Windows hides many file extensions for known file types. To see the extensions for all file types, the user must uncheck the "Hide file extensions for known file types" setting in the Folder Options window. Click on the View tab to see this option.

(Caution: if you change the setting to view extensions, you must make sure that you always retain the same extensions when you change the name of a file.)

It is often helpful to see the file type so that the computer user can identify the program that was used to create the file. Knowing what program was used to create the file is helpful in knowing what program to use to display the file contents. For example, you may receive an attachment to an e-mail message that contains the following file name: filename.ppt. When you try to display this file, you cannot open it. You wonder why you cannot see the contents of this file. If you could find out what program was used to create this file, you would have a better idea of what program you would need in your computer to view it. In the example file shown above, Microsoft PowerPoint program in MS Office was used to create the file. In order to view this file, you would need MS PowerPoint program or MS PowerPoint Reader installed in your computer. Knowing what program was used to create a .ppt file helps you to know what you need in your computer to view or work with the file.

The following Web sites below can help you find the meaning of the extension and the possible program that was used to create the file. With this information, you can determine if you have a program that can display the file or if you need to acquire and install a program.

If you do a search on "file extension" in Google for example, you will find many Web sites that help identify a given file extension. Here are some sites that can help:

FILExt
FileInfo.net
File Extensions Reference
Webopedia