INT 21 - DR-DOS 5+ - DETERMINE DOS TYPE
AX = 4412h
CF set
Return: CF set if not DR-DOS
AX = error code (see AH=59h)
CF clear if DR-DOS
DX = AX = version code
1060h = ???
1063h = DR-DOS 3.41 ???
1065h = DR-DOS 5.0
1067h = DR-DOS 6.0
Note:   this call is identical to AX=4452h

See also: 214452

214412 - DR-DOS 5+ - DETERMINE DOS TYPE