; Possible DOS+ Incompatibilities with CPM 2.2
;  - The IX and IY registers are used, and restored to user values
;    on function exit.  Bios calls from DOS+ are protected.  DOS+
;    does not use the alternate register set.  Interrupt systems
;    that modify and do not restore IX & IY will cause failure.
;  - SYS (T2) attribute automatically marks files non-writable.
;  - The CTL-S pause mechanism always works.  Programs that depend
;    on 2 char input buffering (DOS buffer and hardware) may fail.
;  - Console output chars 0fch and 0fdh are now input on function 6.
;    Compatibility mode inhibits this feature.
;  - Buffered console input (function 10) treats DEL/RUBOUT as BS,
;    and does not implement the ^R repeat line operation.  Will not
;    end a line when full, refuses chars until <cr> entered.  Marks
;    line end with a 0 byte.  Thus max length 1 less than original.
;  - Version returned is 2x, where x is DOS+ revision (4 up). Values
;    in hex. This allows discrimination against CPM2.2, and avoids
;    confusion with CPM3.  The compatibility bit forces 2.2 value.
;    Note that call #210 with e = 0 will always return a non-zero
;    value, so that DOS+ can be detected in compatibility mode.
;  - Files written with more than 65536 records will not be legible
;    to CPM2.2 systems (but will be to CPM3 systems).
;  - Time stamp directory entries may appear as peculiar file names
;    on user 33 to some utilities.  CPM2 and 3 will not access them.
;  - The date/time file stamp format is INCOMPATIBLE with CPM3.
;    dates will be garbage data if read there (and vice-versa).
;    This is caused by maintenance of 3 (not 2) dates with DOS+
; NOTE: The following do not agree with CPM2.2, but DO agree with
;    Digital Researchs CPM 2.2 documentation
;  - Console status call returns 0ffh for ready, rather than 01
;  - SYS files on user area 0 are visible to all users
;
; Added features can be enabled/disabled by the following data:
;  - Enable PATH by putting address of PATH in offset 14H. If this
;    value is 0 no path is used. Suggested value 046H.
;    NOTE power-on cold-boot should clear the PATH string (0 at Path^)
;  - Enable DOS+ time and date stamping with a suitable (non-zero)
;    data address at offset 16H. Suggested value 040h (5 bytes used).
;  - Enable other features with the flag byte at offset 18h:
;    MSB 76543210 LSB
;        ^^^^^  ^----	1 = Echo console to list.  ^P complements
;	 |||||		    (this locn allows applications to control)
;	 ||||^-------   1 = compatibility bit.  Causes verno call to
;	 ||||		    return 2.2. Disables fc/fd operand on DCIO
;	 |||^--------   1 = do file access time stamp (timeat <> 0)
;	 |||		    (disable caters to wrt-protected disks)
;	 ||^---------   1 = enable break on DCIO (if following bit)
;	 |^----------   1 = enable user break, 0 = disable (see 19h)
;	 |		    When disabled ^C will not abort either.
;        ^-----------	0 = time address is location of time array
;			1 = time address is location of routine
;			 (when non-0 address in offset 16h only)
;	(value x10x1000b for maximum CPM2 compatibility)
;  - If user breaks enabled, the char at offset 19h will break.
;  - CCP+ can access wheel byte, suggested location 045h. This allows
;    path/wheel to be initialized by "lxi h,0ffh; shld 45" in bios.
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