Concept of File Extensions


File Extensions:

Standard file extensions following the names of files can indicate whether a particular file is a program or data file. If it is a data file, the extension can indicate the application category that might be used to edit the file. Many common file extensions are three characters long, although there is no longer a strict character limit for the file name or extension in most modern operating systems. A period separates the extension from the file name itself.



Figure: File extensions.

Common File Extensions

The following table lists a number of common file extensions. Because Windows uses the file extension to determine how the system will use a file, if you alter a file name extension, you might find that a program file will not execute properly or that a data file will not automatically open in the associated application.

File Extension and Description

.txt – A plain text file containing no formatting. Can be opened in any text editing program, such as Notepad, or word processing programs, such as Microsoft®Word.

.rtf –  Rich Text Format, a text file that can include a limited amount of formatting such as bold and italic. Can be opened in various applications such as common word processors or Microsoft’s WordPad accessory.

.doc – A data file created in a word-processing program such as Microsoft Word or WordPad. You might also see .docx, an Office 2010 format.

.bat –  A batch file; a small text file containing a list of system commands that execute in a “batch” rather than requiring the user to type each one in succession.

.bin –  A binary file, containing only binary data (1s and 0s), which cannot typically be opened and read by a user application.

.com –  A command file or compiled application file.

.exe –  Executable files that launch programs and applications.

.dll –  A Dynamic Link Library file, containing additional application settings or functions that are loaded by executable files as needed.

.hlp, .chm –  Help files used by various applications.

.htm, .html –  HyperText Markup Language (HTML) files, used to create webpages.

.inf –  Setup configuration settings for operating systems and applications.

.ini –  Configuration settings for software and hardware components.

.msi – A Windows Installer package; a file that can specify installation parameters for an application.

.sys –  System files. System files are typically hidden, as their deletion can prevent the computer from working properly. With system files, it is not just the extension that is important because it helps the computer recognize it as a system file, but the location as well.

.tif, .jpg, .jpeg, .gif, –  Graphic image files in various formats.

.bmp, .png , .xls, .ppt, .mdb –  Data files created in Microsoft®Excel®, Microsoft®PowerPoint®, and Microsoft®Access™, respectively. Office 2007 and Office 2010 allow for .xlsx, .pptx, and .mdbx files.

Viewing File Extensions

How You Do It

1.      Open the folder containing the Windows system files.  

a. Choose StartComputer.

b. Double-click the C drive.

c. Double-click the Windows folder.

2.      Display the file extensions.      

a. On the menu bar, choose OrganizeFolder and search options.

b. Select the View tab.

c. Uncheck Hide extensions for known file types and click OK.


3.  Examine the file extensions.

a. Scroll down to view the files.

b. The first few files in the window have a number of different extensions.

c. To see all the files in a list format, right-click in an open area and choose ViewList.

d. To see similar extensions grouped together, right-click in an open area and choose Sort byType.

e. To return to the default view, right-click in an open area and choose Sort byName.

f.     Close the window.

                                                             ———————- Thanks


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