What are File Types?

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Did you ever try to open a file and the computer wouldn’t let you?  Did you ever wonder what those three or four letters mean after the dot (i.e. period) in a file name?  Well, it all has to do with “file types” also known as file “formats”.  And the purpose of my article is to give you a good basic overview of “file types”.

Why are there different “types” of files?  Well, there are many different programs out there that can run on your computer.  These programs are written by different people and different companies.  If you use a program to create (and save) a new file you will generally need that program to open or use that file.  For example, if I use the Paint program to create a drawing, and I save that file in the “My documents” folder, I will need to open the Paint program again to see that file.  If I give that file to someone else, that person needs to use the Paint program on their computer to open and see my drawing.  In another example, if I create a spreadsheet using the Excel program, I will need to use the Excel program to open that spreadsheet.  That’s not too hard to understand, is it?  The problem is when you try to open a file you did not create on your computer. Suppose, for example, someone sent you a file attached to an email.  You need the right program to open that file.

What are some common “file types”?  Here are some common file types and the code (three or four characters after the dot in a file name) that is used for each:

.bmp – Microsoft Bitmap image (created by the Microsoft Paint program)

.doc – Microsoft Word document (2003 version)

.docx – Microsoft Word document (2010 version)

.exe – an “executable” file (i.e. a program)

.html – Hypertext Markup Language (used for creating web pages)

.jpg – Photo, picture, or drawing image

.mpg – a movie or video

.pdf – Portable document format (Microsoft WordPad program)

.ppt – Microsoft Power Point

.rtf – Rich Text Format, a basic text file

.xls – Microsoft Excel spreadsheet

And there are only a few thousand more!  You can get the huge list by using Google and entering “file types” or you can learn about a particular file type by entering it in Google as well.  The point here is that if a program can create a file you need the same program to open or use that file.

Now having said all that, there are programs than can open and save more than one file type.  If you have a digital camera and take photos, for example, each photo is a file and each photo is probably a “.jpg” file (or file type).  But there are MANY programs out there than can open these types of photo files and work with them – Picasa, FastStone Image Viewer, Windows Photo Viewer, Adobe Photoshop, and the Paint program are just a few.  They can all open and work with .jpg photos.

On the other side of the coin, a program may be able to save the same file as different file types.  For example, if I create a new document using the Microsoft Word program, when I save the file (using “Save as…”) I can select from several file types at the bottom of the “Save as…” window.  If you left-click your mouse on the small black triangle arrow at the right end of the “Save as type” box you will get a list of the different files types that Microsoft Word can use to save your document – such as “rich text format”, “plain text”, or other old versions of Microsoft Word.

So here are the key lessons for today:

  1. If you use a program on your computer to create and save a file you will always be able to open that file again because you have the program that created it to begin with.
  2. If you try to open a file that you did not create (such as a file someone sent to you via email) you may not be able to open it unless you have a program on your computer that can open that file type.
  3. If you receive a file from someone that you cannot open, contact them and ask them what program they used to create that file.  If you do not have that program, ask them to send the file to you in a different format – one that you can open with a program you do have.
  4. Use Google to find out more information.  Perhaps there are some free programs on the internet that will allow you to “open” and “read” a file.

Hopefully this is not too difficult to understand.  It really is not the computer’s fault (this time, anyway) and it’s not your fault either if you cannot open a file someone else has given you.  It’s like someone giving you a machine made in another country which uses the metric system.  You will need metric tools to work on that machine.  Or maybe I can just ask my mechanic for help.

Jim Cerny, Director, Sarasota PCUG, Florida

May 2013 issue, Sarasota PC Monitor

www.spcug.org