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121. File Types: The Power of a Name

By Andrew D. Wright

Names have power. In many old stories and traditions to know the true name of someone was to have control over them.

On Windows-based computers, most files have a true name that is hidden from you by default. This true name usually ends in a three letter extension, a handy hold-over from Microsoft's early MS-DOS days.

What a Windows file is and what you can do with it will depend on this extension. Some files, such as text files with a TXT extension, are harmless. Other files can be dangerous.

The first thing to do is set your Windows Explorer to show these file type extensions. Once you can see them, you'll have a powerful tool in your computer arsenal.

Open Windows Explorer by pressing the Windows key on your keyboard and the letter e at the same time. If your keyboard does not have a Windows key, usually set between the Alt and Ctrl keys on the bottom row, then go to the Windows Start button then Run and type in: explorer then hit Enter.

When Windows Explorer opens, click on Tools then Folder Options. Select the View tab and uncheck the box marked: Hide extensions for known file types. Click OK and next time you open Windows Explorer (or browse your files through the Windows Explorer interface) you'll see the file type extension in the file names.

In MS-DOS, Microsoft's first operating system, all file names had to be no more than eight letters long with a dot and a three letter file type extension at the end.

With the release of Windows 95, this restriction was lifted and files could be named anything. Underneath the hood though, Windows kept a record of files in the old eight letter: three letter format.

By now most people are familiar with a number of different data formats, even if they are not computer people. An MP3 file is an audio file format, a JPG file is a picture and so on.

These days the file extension does not have to be limited to just three letters, but most file names keep to this rule anyway.

Some file types are called executable, which means that the file is a program that can run commands on your system. The most common executable file types are: BAT, COM, EXE, PIF, and SCR. There are a couple of dozen file formats that can be considered as executable so it is a good idea to check if you are not sure what a file is, before clicking on it to run it.

Windows knows about many file extensions but is a bit thick when it runs into one it doesn't know. Unfortunately the Windows file extension lookup service is not very good. The best idea is to open a search engine and do a search for the file type. This will usually give you information on what kind of file you have and what program would be needed to open it.

To associate a program to open a particular kind of file Windows does not know about, or change a program association already set in place, open Windows Explorer and right click on the file. Select Open With and look at the list of programs Windows suggests using to open the file.

Click Choose Program and browse your computer to find the program folder and the EXE program file. Clicking on the little check box that says to always use the selected program will set things so just double clicking on that file type in the future will open the file using the program you have set.


Wikipedia's List of File Extensions:


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Originally published 14 December 2007


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