The virtual display device provides the following general services:
VDD_Clear_Mod
VDD_Free_Grab
VDD_Free_Mem
VDD_Get_GrabRtn
VDD_Get_GrbMem
VDD_Get_Grb_State
VDD_Get_Mem
VDD_Get_Mod
VDD_Get_ModTime
VDD_Get_State
VDD_Get_Version
VDD_Hide_Cursor
VDD_PIF_State
VDD_Query_Access
VDD_Set_HCurTrk
VDD_Set_VMType
VDD_Unlock_App
When a virtual machine is created, the virtual shell device calls the VDD_PIF_State and VDD_Set_VM_Type services to notify the VDD of the user preferences for the virtual machine. Other general services are used by the 386 enhanced mode display grabber and the virtual mouse device to retrieve information about the state of the display.