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File Extensions and You: A Cautionary Tale

Everyone has been there. You're hanging out with your friends, talking about, you know, whatever, when someone makes a joke with the perplexing punchline, “...and I said '.BMP? More like .DUH!'” Your friends all laugh, but your forced chuckle earns you incredulous stares from all sides. “Don't you get it?” they want to know. “Like, file extensions,” they explain, disappointment thick in their voices. But they can tell you don't understand. Afterwards, they start calling you less and less often until your phone finally goes permanently silent. Tortured by your shame and loneliness, you eventually change your name to “Mr. Mojo Risin” and move to Paris in a vain attempt to escape the abominable memory of their scornful faces. Like I said, we've all been there.

Fortunately, you've found this handy guide to basic Windows file extensions which will prevent such irreparable social disasters – unless, of course, you're tearfully reading this from a dingy hotel room in the Place de la Bastille, in which case we offer our sincerest condolences, Mr. Risin.

File extensions in Windows are brief suffixes appended to a file's name (separated by a period) that let the computer know what type of file it is. So, for example, the file “filename.duh” is a “.duh” file; double-clicking such a file tells Windows to open the application associated with .duh files.

There are innumerable file extensions, but it is far from necessary to know all of them. In fact, Windows has hidden file extensions by default since 3.1, so if you've never heard of them, there's a good reason. If you haven’t done so already, unhide file extensions in your computer. In Windows XP, go to Windows Explorer, click the Tools menu, then Folder Options. From there, click on the View tab, and in the Advanced Settings box, find and uncheck Hide extensions for known file types.

Revealing file extensions in Windows XP
Figure 1: Revealing file extensions in Windows XP

In Vista, the process is the same, except that you get to the Folder Options menu through the Control Panel.

Different types of files (such as image files, music files, video files…) have different file extensions associated with them, so let’s take a look. We'll begin by listing a few common image file extensions.

  • .BMP – This is the Cadillac of image file extensions; it's big, it's beautiful, and your grandfather probably drives one. BMP is short for “bitmap,” and these files are huge (from a file size standpoint) uncompressed (thus high quality) images that have been around since computers could display pictures. If you've ever used Microsoft Paint, you've used these.

  • .JPEG or .JPG – JPEG files are compressed (and thus lower quality) images that have become the standard Internet file type because of their favorable file size to quality ratio. They can suffer from “compression artifacts” (usually identifiable as a sort of uneven graininess scattered around the picture) if they're not encoded well, so graphic designers and photographers tend to prefer other file types.

  • .GIF – Another web standby, the GIF is notable for being a lossless compressed image file (as opposed to the JPEG) that can store frames of animation, making it ideal for putting spinning pentagrams on your poorly designed KISS fansite.

  • .TIF or .TIFF – This is a file extension usually used by graphics editors such as Adobe Photoshop or Corel Painter. TIF files can support layers (the computer version of painting on layers of clear celluloid), and also have a form of lossless compression that makes them ideal for high-quality images and printing.

There are several other extensions for image files, but those are the most common ones. From there, let's move on to a few common audio files.

  • .MP3 – Probably you know what these are. Probably you have a few gigs worth stored on your iPod even as you read this. Probably you don't need me to tell you that it stands for MPEG-1 Audio Layer 3, or that it's a type of compressed audio file made wildly popular with the advent of peer-to-peer file sharing. Because you already know all that, don't you?

  • .WAV – The BMP of audio, these are fairly old, fairly huge uncompressed audio files. While once fairly ubiquitous, they have been largely superseded by MP3s and other compressed audio files because, while WAVs' audio quality is higher than MP3s', they are also usually several times larger than their newer, sleeker competitors, and thus more cumbersome to download or store on tiny, hip pieces of consumer electronics.

Those two are by far the most common audio file extensions. There are, again, several more file extensions for audio files, but if you know MP3 and WAV, you'll be alright in most social situations. With that covered, there are just a few more miscellaneous file types to go over before you're ready to impress your friends at the next cocktail party.

  • .EXE – You'll see this one a lot. It stands for “executable,” which means it's a file you can run. Most programs you use are EXEs, since it's the most common type of application file, so you've definitely run into these before. One thing you shouldn't do is run an EXE if you don't know where it came from, since most viruses are packaged as EXEs. That's like drinking an open soda you found on the side of the road, which is generally considered a bad idea.

  • .TXT – This extension represents a simple text file. TXT files are usually pretty simple with regards to fonts, formatting and the like. This is the default file extension for Windows notepad, so you've probably seen these before.

  • .DOC – TXT's big brother, this document file is commonly associated with Microsoft Word, though just about any other word processing program can read it. It stores not only text, but also detailed formatting information, embedded images, and many other fancy accouterments that the present-day word processor demands. Microsoft Office 2007 has introduced a pretender to the standard document file type throne, the .DOCX file, which has met with some criticism due to its incompatibility with older versions of Office. Microsoft has released a fix for this issue, but it's still more cumbersome than simply opening a plain old DOC file.

  • .XLS – This is a spreadsheet file, most commonly used with Microsoft Excel, but, again, openable by most spreadsheet applications (such as Openoffice Calc, for example). Microsoft also sought to replace XLS in Office 2007 with XLSX, and, again, there is a converter fix to make the newer files work on older software, but there is still lots of grumbling from consternated cubicle dwellers across the globe.

  • .PPT – If you've ever fallen asleep during a business meeting while a projector displayed needlessly animating slides, then you've seen PPT files in action. This is the default file type of Microsoft's PowerPoint, and young professionals eager to make a good impression on upper management owe this file type their continued employability. Microsoft, years after even Mountain Dew's advertising started to seem slightly embarrassed and apologetic about the “X- Treme” marketing craze of the late 90's, decided to also append an “X” to the end of the venerable PPT file for its 2007 version of Office, but the much-sought- after 18-to-35-year-old male demographic is largely unimpressed.

That's it for the basic file types, but what can you do if, for some unknown reason, Windows Picture and Fax Viewer gets set as the default program to open MP3s? Well, there are a few things you can do. The first, and probably easiest, is to right-click on the file of choice, then select Open With, and from there click Choose Default Program (in XP, this is merely Choose Program), which enables you to choose your program from a list, or to browse for it (in XP, you will have to check the Always use this program to open this type of file box).

Selecting program to use
Figure 2: Selecting program to use

Another method in Vista is to go Control Panel > Default Programs > Associate a file type or protocol with a program.

Associating a file type in Windows Vista
Figure 3: Associating a file type in Windows Vista

That will bring up a list of all the file extensions you've ever seen on your computer (and probably many you haven't), and you can select any of them and click the Change Program button; but be warned: if you select a program that can't open the file you want it to, you'll have to go back and redo the change, wasting up to a whole minute of work.

Exam Tip: Pretty much every file type has an associated extension. The little Control Panel icons you click on to run programs such as Default Programs in Vista, for example, use the file extension .CPL. Good to know for those rare occasions you’d need to search for one or disable one. Even Windows Help files have a standard extension, .CHM.

So there you have it. While this brief rundown won't make you a file extension expert, it will at least give you a pretty good foundation for bluffing your way through the various file extension jokes that are so popular among today's youth. File extensions are no laughing matter, however, and taking these to heart may just save you a one way plane ticket to Paris.

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