INT 15 - Far East MSDOS - GET DOS TYPE
AX = 4900h
Return: CF clear if successful
AH = 00h
BL = type of DOS running
00h DOS/V
01h DOS/J or DOS/K (early IBM Japan versions of MSDOS)
CF set on error
AH = 86h (function not supported)
Note:   in practice, DOS/J returns AH=86h; AX DOS does not support this call

See also: 2130

154900 - Far East MSDOS - GET DOS TYPE