INT 15 - later PSIBM PS/2, any model/2s - GET NUMBER OF DEVICE DESCRIPTOR TABLE (DDT) ENTRIES
	AX = D100h
	DX = 0000h (reserved, must set to 0)
Return: BL = size of one DDT entry, in bytes
	CX = number of DDT entries
	AH = return code (see #00534)
	CF set on error
	CF clear on success
SeeAlso: AH=C0h,AH=C7h,AH=C9h,AX=D101h,AX=D102h,AX=D103h,AX=D104h


(Table 00534)
Values for return code:
 00h	success
 01h	requested DDT entry not found
 02h	DDT data not valid
 86h	function not supported