The hardware-abstraction layer. Consists of hardware and device driver mechanisms that insulate applications from device-specific implementation details. If a capability requested by an application is not implemented by the current hardware, the capability will be emulated by the software.
The hardware-emulation layer. Provides software-based emulation of features that are not present in hardware.
In DirectPlay, a virtual player whose ID is DPID_SYSMSG. System messages and messages sent to all players in a session are managed by the host.