Int 7A Fn 09  - IBM 3270 Workstation Program API - Session Services        [I]

   AH = 09h
   BX = 8020h (synchronous request)
   CX = 0000h
   DX = ID of session manager (SESSMGR)
   AL = service
       01h get session ID
       02h get session info
       04h dettach from session
       05h attach to session
       06h get list of windows available
       07h get environment of window
       08h get 'PIF' (program information file) info
       0Ah get base window ID
       0Bh get cursor info
   ES:DI -> control block

Return: ???