extension (EXTN)

The term extension is used in different contexts: As a hardware extension of cables or as extensions for file formats.

1. An extension can be a hardware extension in the form of a cable or a plug-in device.
2. Extension means in combination with file formats and programs an addition to the file name. This addition is also called a suffix and is added to the file name as a file extension. An extension is a two-, three- or four-letter suffix appended to the file name or program name and separated from it by a period. It characterizes the file content. The operating system and the application program can distinguish between different file types by means of the extension, which depends on the operating system. The extension is automatically appended by the application program when saving.
3. Extensions usually describe a defined file format, for example for text files (*.txt, *.doc), for graphic and image files (*.ai, *.cdr, *.tif, *.bmp, *.wmf), for compression files (*.jpeg, *.mpeg), for audio and video files (*.aiff, *.midi, *.avi), for exchange formats (*.pdf, *.rtf, *.dxf) and for Internet file formats(*.gif, *.png, *.html) to name just a few of the several hundred.