Understanding File Extensions

A file extension is the “suffix to the name of a computer file” (Wikipedia). It is usually a 3 or 4 character ending that appears after the period (filename.fileextension). It is important to understand file extensions to know whether a computer can open a certain file. Below is a list of four common file extensions and the software needed to open them.

filename.doc	Microsoft Word (versions 97-2003) uses the .doc file extension. A computer needs Microsoft Word installed to open these files. Mentioned previously, a free alternative to Word is OpenOffice that will also open .doc files.
filename.docx	Microsoft Word (version 2007) uses the .docx file extension. A computer needs Microsoft Word 2007 (the newest version) to open these files. (OpenOffice will work as well.)
filename.rtf	.rtf stands for Rich Text Format. It is a more general file format that most word processing programs can open including WordPad and Notepad (both of which come pre-installed on PCs).
filename.pdf	While the above three file formats will open in a word processing program and allow changes to be made, a .pdf file opens with Adobe Reader. Once opened in Adobe Reader, the user can only view the document. No changes can be made. Adobe Reader is a free download. To get the latest version, go to http://get.adobe.com/reader/.

When sending files through email or making them available on Blackboard, we recommend using .rtf or .pdf, since both can be opened with software that doesn’t cost money.