COMMAND.COM is the filename of the efault operating system shell for DOS operating systems and the default command line interpreter on 16/32-bit versions of Windows (9x/Me). It has an additional role as the first program run after boot, hence being responsible for setting up the system by running the AUTOEXEC.BAT configuration file, and being the ancestor of all processes. COMMAND.COM's successor on OS/2 and Windows NT-based operating systems is cmd.exe. COMMAND.COM is also available on those systems to provide compatibility when running DOS applications within the NT Virtual DOS machine.