A+ Certification / Beginners

Understanding file extensions

In this section, some of the major types of file extensions you can expect to see within your operating system. By default, file extensions for registered file types are hidden. Registered files types are files that have extensions which already have applications associated with them. To display file extensions within Windows XP, follow these steps:

  1. Open any directory window, such as My Computer.
  2. Choose Tools → Folder Options.
  3. Click the View tab.
  4. Clear the check box in front of Hide Extensions for Known File Types.
  5. Click OK.

In the sections that follow, we discuss common file extensions and how they are used on your computer.


Executable files can perform tasks on the system. Table below summarizes some of the file extensions common to executable files.

Executable File Extensions
.batBatch fileBatch files are a series of commands that have been sequentially typed into a text file.
.cmdOS/2 command fileCommand files usually execute with only a command shell interface.
.comMS-DOS command fileLike the OS/2 command files, these files usually execute with only a command shell interface.
.exeCommand-line or graphical programThis is the most common extension for executable files.
.vbsVisual Basic Script fileVisual Basic Script files are not executable themselves, but rather require either wscript.exe or cscript. exe to be executed. They are a cross between Visual Basic applications and batch files.

Major Office applications

You need to be familiar with the file extensions associated with a few of the most popular office applications on the market. Some of these extensions are listed in Table below.

Application File Extensions
.docDocument FileDocument files are usually associated with Microsoft Word, but are sometimes used by installations of WordPerfect.
.dotDocument templatesDocument templates for Microsoft Word. normal.dot is the default template for new documents.
.ppt, .ppsMicrosoft PowerPoint documents.ppt files open in the PowerPoint interface and are immediately editable. .pps files, when you double-click them, open directly in PowerPoint Slide Show mode and close as soon as the slide show finishes.
.wks, .wk4Lotus 1-2-3 worksheet filesThe number at the end denotes that a specific version of Lotus 1-2-3 was used.
.wpdWordPerfect documentThis and .doc are common extensions for documents.
.wpgWordPerfect GraphicWordPerfect's proprietary graphic format.
.xlsMicrosoft Excel documentSpreadsheets associated with Microsoft Excel.
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