Int 21 Fn 3000  - Ctask 2.0+ - Installation Check                          [T]

   AX = 3000h
   BX = 1234h
   DS:DX -> 8-byte version string (DX < FFF0h) "CTask21",00h for v2.1-2.2

Return: AL = DOS major version
   AH = DOS minor version
   CX:BX -> Ctask global data block
Program: CTask is a multitasking kernel for C written by Thomas Wagner

Note:  if first eight bytes of returned data block equal eight bytes passed
     in, CTask is resident