A feature in personal computers that runs a program on a CD/DVD or USB drive. AutoRun is considered a security risk because a virus could be unleashed when the medium is inserted, which is why it is no longer the default in Windows. The Mac AutoStart equivalent was also dropped in Mac OS X.
AutoPlay is the Windows dialog box that appears when an external medium is inserted, offering the user options to play, run or view the content. The terms AutoRun, AutoPlay and autostart are used synonymously; however, autostart may have other meanings. See autostart routine