File Extensions and Registered Programs

Everything that you do on a computer involves files of one type or another.  There are program files and library files that make your software run.  There are data files that your software creates.  Documents, spreadsheets, mp3s, videos, databases – all these are files.

On a Windows computer, each file name has what’s called an “extention” that identifies what kind of file you’ve got.   For example, .doc is the extension for windows documents, and the file names would be “something.doc”.  Excel spreadsheets have the extension .xls and the file name would be “something.xls”.  (Office 2007 has introduced some new files extensions, but I’m using the old ones so more people can follow.)  Mp3s have the file extension, well, .mp3, so you can have a filename “coolsong.mp3″.  Videos can have a number of extensions:  .wmv, .avi, .mpg, .divx, .mp4, .m4v and others.

Out of the box, windows doesn’t show the extensions to the file names.  In order to see them, do the following:

1. Open  My Computer, or any file window, like your C-drive, or My Documents.

2. Click the “tools” menu, then slide down and click “folder options”.

3. Click the “view” tab, and you’ll see the option for “Hide extensions for known file types”.  If that is checked, your system won’t show the extensions to the files on yoru computer.  Uncheck them, and you can determine the type of file from the extension.

Different extensions are set up to open in different programs in Windows, so you can just double-click the file to open it in the software that’s set to handle it.  So if you double-click a .wmv file, it usually opens in Windows Media Player.  “Wmv” stands for “Windows Media Video” by the way.  A .doc file, will open in Microsoft word when its double-clicked, or if you don’t have Word installed, will open in a small Windows program called Wordpad.

You can right-click a file, and force it to open in a program other than the default program for that extension.  So for example, if you want to open a .wmv file in, say, the DivX video player, you can right-click the file, and scroll down to where it says “Open With”.  At that point you will be presented with one or more options of programs that Windows knows will open the file.  If the program isn’t in that list, you can click “Choose default program” at the bottom of the menu.  You’ll see a “browse” button, and you can then go to the program you want to use to open it.  Most of your programs are in C:\Program Files, and then you can find the folder you want, and click the executable file (.exe) for that program.

If you leave the check mark next to “Always use the selected program to open this kind of file”, you change what program Windows will use to open that file by default.  This is referred to as the “registered program” for that file extension.

That’s a little bit about files.  There’s more to come in my next post about how to name files in an organized fashion.

Stay tuned!