Question:     What is a "file extension" and why does my computer sometimes ask what

                        program do I wish to associate with a particular file extension?

Answer:        The group of letters after a period or "dot" in a file name, is called the "file

                         extension". This extension refers to the type of file it is. For example, if the

                         filename is readme.txt, the extension "txt" denotes this is a text file and can

                         be viewed using a text editor such as Notepad or a word processor such

                         as Wordpad or Microsoft Word. The name of the file is "readme".

                         Operating systems such as Windows will refer to a file's extension

                         when choosing which application to launch when a user clicks on a

                         particular file name.

                         It is important to understand that most files need a program to open or

                         display them, and if you do not have the correct program for that file

                         extension, your computer will prompt you for the name and location of

                         the program you wish to use. At this point you are usually in trouble,

                         because if windows can't figure out how to open the file, it is a good

                         bet that you can't either.

                         To try to explain this further, I have listed a number of common file

                         extensions, what they are and what kinds of programs are

                         required to open them:

                         Extension                    File Type                                Program Needed to Open      

                            .txt                               Text File                               Notepad (or word processor)

                            .doc                             Document                             Wordpad, Microsoft Word

                            .jpg                              Picture (Image)                     ACDSee

                                                                                                             Adobe Photoshop

                                                                                                             Microsoft Paint

                            .xls                             Spreadsheet                           Microsoft Excel

                            .pcp                            Flyers, Greeting Cards           Broderbund Print Shop

                            .pub                            Flyers, Greeting Cards           Microsoft Publisher

                            .mp3                           Sound File                             WinAmp

                                                                                                             Windows Media Player

                            .pps                            Slide Show                            Microsoft Powerpoint

                       Some files (extensions) can be opened by many programs, such as an

                       image file (.jpg) or a sound file (.mp3) and some files can be opened only

                       by the program that created them. Example of this would be ".pdf" files

                       created by Adobe Acrobat.

                       To further complicate the subject of file extensions, there are some files that

                       do not require a program to open them. These are called "executable" files

                       and have the extension ".exe", or "batch" files and have the extension ".bat". 

                        There are many, many programs creating files with different file extensions.

                        If you didn't create the file with a program on your computer, there is a

                        chance you will not be able to open the file. You may receive a file in your

                        e-mail, and click or double click on the file and get the message asking

                        what program do you wish to use to open the file. 

                       If you are unfamiliar with the file extension, you can go to the following

                       web site to find out more about the file:     www.filext.com

                       Another item to note, is that the default set up in Windows is to hide common

                       file extensions. This can be confusing to some of us and I suggest you

                       change this by setting Windows to show ALL file extensions. To do this, go

                       to "My Computer" and click on the drop down menu "Tools". From this

                       menu, click on "Folder Options", then the tab "View". In this list, take the

                       check mark out of "Hide Extensions for Known File Types". Click "Apply"

                       and then "OK" and you will see the file extensions for known file types also.