Extension
1. In general an extension is a part that is added to something that extends or enlarges it. For example, in the case of computer cables an extension cable or extension cord is a cord capable of being connected into another cord that extends its overall length. A common example of extension cables used with computers are power extension cords, USB extension cable, DVI/VGA extension cable, and network extension cable. There is an extension cord for almost every cable ever made. However, keep in mind that most cables also have length limitations. Most specialty computer stores and online retailers have extension cords that can be purchased at various lengths.
2. When referring to an IBM compatible computer's files, a file extension is the three characters after the file name. See our file extension definition for further information on this term.
3. When referring to an Apple Macintosh computer, extensions or system extensions are files that are stored in the extension folder that load into memory when the computer first loads. Extensions were known as an INIT on System 6 and earlier.
Also see: Apple definitions, Association, File extension, INIT, System