Know Your Extensions

Did you know that when you save a file the computer automatically adds a period and three letters to the end of the name you give the file.  In the old days, before the Windows operating system, file names used to look like this:

Technically speaking, file extensions like:  .exe, .bmp, and .log are still being used by your computer.  However they might not always be displayed with the file name.  They are still important because they tell the computer what program to use to open a file.  Below are some common file extensions that you might see and the programs that opens them:
Extension     Program that opens it
.doc     Microsoft Word
.xls      Microsoft Excel
.pub     Microsoft Publisher
.ppt      Microsoft PowerPoint

Some file extensions, especially the ones used on the internet, tell you what kind of file something is.  Here are some examples:
Extension     What it probably is
.htm     A web page
.gif       A Graphic or Animation
.jpg      A Photograph or Image
.png     A Photograph or Image
.mpg     A Movie or Animation
.pdf       A Portable Document File
.mp3     A Sound or Music File