File extension

A file extension or filename extension is a suffix at the end of a filename. It is used to show the type of computer file. This tells the operating system what program can understand it. For example, MYWORDS.TXT is a plain text file and may be opened by a text editor. Filename extensions come after the name of the file, and many of them are three letters long. 

Some examples of common file extensions are:
 TXT files are plain text files
 Picture files
 BMP are bitmap picture files
 JPG are picture files in the JPEG format
 Audio files
 MP3 are music files in the MP3 format
 AAC are Advanced Audio Coding music files
 FLAC are Free Lossless Audio Codec
 ALAC are Apple Lossess Audio Codec
 WMA are Windows Media Audio sound files
 MPEG are motion picture encoded video files
 MKV are Mastroska Video Codec
 WMV are Windows Media Video files
 HTM or *HTML are Hyper Text Markup Language files such as web pages
 PHP are web server scripts which create web pages
 ODT are Open Document text files
 DOC are text documents in Microsoft Word format
 XLS are Microsoft Excel spreadsheet documents
 PPT are Microsoft PowerPoint presentation files
 EXE are Microsoft Windows executable program files
 DLL are Dynamic Link Libraries, a type of executable file, in MS Windows
 ZIP are Compressed files (Lempel Ziff algorithm in an archive)
 Z are Unix / Linux compressed files
 bz2 are bzip2 block compressed files (very good compression)
 jar are Java archive files
 JSP are Java server pages files
 java are Java source code files
 class are Java compiled source code files
 oc are Java run-time library files
 tar are Unix / Linux tape archive files
 sh are Unix / Linux shell script files
 awk are Unix C like pattern processing language source code files
 sed are Unix stream editor command files
 lex are Unix / Linux lexical analyzer C code generator specification files
 c are C programming language source files
 o are C programming language compiled (object) files
 cs are C# programming language files
 v are V programming language source files
 vsh are V programming language script files
 rb are Ruby programming language files
 pl are Perl or Prolog programming language files

There are many other commonly used file extensions.

In most operating systems, you can change the program defaults so that the computer knows which program to open each type of file extension with.

Category:Software
Category:Computer file formats