FILE EXTENSIONS

We’ve all often wondered what the three letter extension on some of our files mean. File extensions are your files’ "last names" and understanding their meanings will allow you to better manage your files. You may be viewing your files with the default setting for Windows and so are not seeing these extensions at this time. To change that, do the following.

In Explorer, select View from the toolbar. Click on the box for "Hide file extensions for known file types." The file extensions will now be shown. Some common file extensions are as follows:

.EXE executable (or program) files If you click on an EXE file, you’ll run a program. But be careful, as many viruses are propagated by seemingly harmless EXE files.

.COM a program file Before the dot coms of the Internet, "com" meant compiled. Like an EXE file, a COM file is a program file. Apply the same precautions as you would in opening an EXE file.

.TXT text files These files can be opened with just about any word processor because they are text only, with no formatting.

.DOC MS Wordprocessing files A DOC(ument) file will open in either MS Word or WordPad. Unlike TXT files, DOC files retain all formatting information. (These files can also harbor viruses, within macros which are small programs that automate steps within Word. Be wary of files that ask you to enable macros, as they may launch viruses.)

.WPD WordPerfect files A wordprocessing document created in WordPerfect.

.HTM (or HTML) hypertext markup language file The language of the World Wide Web, an HTM file will open in your web browser and display as a web page, even if you aren’t connected to the internet.

.XLS Excel files A spreadsheet file created in Microsoft Excel.

Common graphics file extensions:

.GIF graphics interchange format file Common on Web cause they can be animated.

.JPG joint photographic expert group (graphics) file More compressed than GIFs without loss of quality.

.BMP bitmap (graphics) file Native Window’s graphic format that are completely uncompressed.

.TIF tagged image (graphics) file Common for scanners, not compressed.

.AVI audiovisual file

.WAV audio file

.MID Musical Instrument Digital Interface file

System Files:

.INI initialization files These tell a program where it was and what was going on when it was last used.

.DLL dynamic link library file Modules for Windows programs, these are installed on your hard drive when programs are installed. To avoid cluttering your system, consider uninstalling old programs rather than deleting them, as this will get rid of old unused DLLs.

.SYS system file These files are used by the system itself.

.HLP help file Used by Windows programs to help with the program.

.TMP temporary files These files can usually be safely removed to save space.

.VXD virtual device driver files These files are used by programs to communicate with printers, modems and other peripherals. Tamper with these files and you may have problems with communications.

.DAT data files

This is by no means a complete list of file extensions. There are many other document, graphics, video and sound extensions from other computer systems and programs. But these are some of the most common and knowing them may help you know your computer a little better.

Source: Alphabet Soup: Deciphering file extensions and their meanings, by Robert P Fox, Legal Assistant Today, January/February 2000