By default, the internal DOS command works by directly calling the corresponding BIOS function to clear the screen, thereby prominently violating the hardware abstraction model otherwise maintained. However, if an ANSI driver is detected by the DR-DOS , it will instead send the control sequence defined in the reserved environment variable to the attached console device. If the environment variable is undefined, it falls back to send the sequence instead. Specifying other sequences can be used to control various screen settings after a . Due to the difficulties to define environment variables containing binary data COMMAND.COM also accepts a special notation for octal numbers. For example, to send an alternative control sequence like (for as used by ASCII terminals), one could define the variable as follows: