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File Format
Extension(s) .bat, .dos, .win
Released 1981

AUTOEXEC.BAT is a special batch file that was present in the root directory of a boot disk for various versions of PC/MS-DOS and Windows, containing commands that were excecuted upon bootup in order to complete the setup of the system before the user was placed into the command prompt. If you wished the computer to automatically boot into some particular program you would place the command invoking it at the end of this file where it would run after all the other setup was complete. Modern Windows versions have other means of running things on launch.

Some Windows versions also had a AUTOEXEC.DOS file, designed to run when running the system in standalone DOS mode without Windows; on seeing the proper function key pressed on bootup, the system would rename this to AUTOEXEC.BAT and the original one to AUTOEXEC.WIN, so that the DOS-based autoexec file was used instead of the Windows-based one.