What File Extensions are and How to See Them

File extensions are very important to your computer. They identify the software program that will be used to open the file. When you double click on an icon, the computer looks at the characters after the period on the file name, then uses that program to open the file.

File extensions are the characters after the period in file names or to the right of the period. For example a file might be called LETTER.DOC - The name of the file is LETTER and the extension is after the period, DOC. The extension of .DOC on most computers will open up Microsoft Word.

The other thing that assists you in telling what program will open the file is the icon. Microsoft Word has a big blue W on it, Excel has a green X and so on.

Usually most computers are set up as a default to not show the file name extension, and it really can be a help. When you cannot view the extension you would just see the icon and the name LETTER with no .DOC after it.

If you rename a file, you must put in the extension, otherwise the computer will not know what kind of a file it is and what to open it with.

It is really easy to turn this on so you can see the file extension. This can help if you are having problems opening a file, sometimes the file extension gets removed when it was saved or renamed.

In Windows XP
open up a folder such as My Documents
Click on Tools>File Options...
Click on the View tab
Uncheck the box that says "Hide Extensions for known file types"
Click Apply, and then OK.

In VISTA
open up a folder such as My Documents
Click on Organize>folder and search options
Click on the View Tab
Uncheck the box that says "Hide Extensions for known file types"
Click Apply, and then OK.

That is it, now you will be able to see those handy little extensions. Next time I will explain how to change those file associations so you can change what program opens with a particular file extension.