16 August 2005

File Associations

Have you ever received an attachment to an e-mail that you cannot open? You get that annoying message: “This file does not have a program associated with it for performing this action. Create an association in the Folders Options in Control Panel.”

The name of any file consists of two parts: the filename and the extension. The first time you save a file in a program, such as a word processor, spreadsheet, or graphics application, you are asked to give it a name. This is the filename. Extensions are those three-letter suffixes attached to all files that let your computer know what kind of file it is trying to open. The filename and extension are separated by a period.

If you view a detailed list of files in a folder, the filename and extension should show. If you do not see the extension, Windows is hiding them. In order to understand the rest of this Tutor Tip, you need to display file extensions. In Windows XP, click Start, Control Panel, and Folder Options (In Windows 98, click Start, Settings, and Folder options.) Click the View tab and remove the tick mark next to “Hide file extensions for known file types.”

A file type (extension) identifies the program that is used to open the file. When a file type is registered with Windows (or Homeland Security), information about which program is used to open that file (by default) is also registered. When you install a program, it tells Windows which extensions to associate with its data files. For example, Microsoft Word uses .doc as its default extension. If you save a file in Word, by default the extension will be .doc. If you have Word installed on your computer and double-click a file with the .doc extension, Windows knows to open it with Word.

If you try to open a file that has an unregistered extension, Windows will not know what program to use to open it. For example, you do not have Adobe Photoshop on your computer. You double-click a file that has the extension .psd (Photoshop’s default). You will get the message: “This file does not have a program associated with it for performing this action. Create an association in the Folders Options in Control Panel.” Indeed, you could create an association, still you do not have a program that can read the file. All you will get is strange happenings in the program.

Therefore, if someone sends you a file as an e-mail attachment and you get that “… program associated …” message when you try to open it, you cannot open it. Ask the person to send it in a format that you can open. For example, most word processors can save files in the format of other common word processors. Failing that, he or she could save it as a “rich text format” (or .rtf). An rtf file can be opened by any word processor and it retains most of its formatting. Failing that, the file can be saved as a plain text file that can be opened by Notepad. If the person cannot or will not send it in another format, have him or her buy you a copy of the program they used to create the file.