INT 7A - IBM 3270 Workstation Program API - HOST SERVICES AH = 09h BX = request type (4000h async, 8028h synchronous) CX = 0000h DX = ID of MFIC AL = service 01h connect to host 02h disconnect from host 03h read DFT structured data from host 04h write DFT structured data to host 05h create a host buffer ES:DI -> control block