## H

HAL
  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.
hardware blitter
  A hardware component, built into the display adapter, that performs efficient blit operations.
HEL
  The hardware-emulation layer. Provides software-based emulation of features that are not present in hardware.
hit detection
  See collision detection.
host
  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.
HREF
  Acronym for horizontal refresh. In a video stream, the HREF is active to signal that the display is to begin a new scan line. See also, VREF.