AUTOEXEC.BAT is the name of a system file foun originally on the MS-DOS operating system. It is a plain-text batch file that is located in the root directory of the boot device. The name of the file is a portmanteau of the words "automatic" and "execution", which describes its function in automatically executing commands on system startup; the portmanteau was coined in response to the 8.3 filename limitations of the FAT file system family.