hardware branch The hardware archive root key in the registry that is a superset of the memory-resident hardware tree. Although the hardware tree contains information only about those devices currently detected and running in the system, the registry contains a complete list of all hardware ever installed on the particular computer. The hardware root key is \\Hkey_Local_Machine\Hardware.
hardware tree A record in RAM of the current system configuration, based on the information for all devices in the hardware branch of the registry. The hardware tree is created each time the system is started or whenever a dynamic change occurs in the system configuration.
HCI Host controller interface. For example, a system-level interface supporting USB.
HCL Hardware Compatibility List. A registry of products that have been tested by WHQL and that have passed Windows compatibility testing.
HCT Hardware Compatibility Tests. A suite of tests from WHQL that verifies hardware and device driver operations under a specific operating environment. These tests exercise the combination of a device, a software driver, and an operating system under controlled conditions to verify that all components operate properly.
HDTV High-definition television. A proposed standard that recommends doubling the current 525 lines per picture to 1050 lines, and increasing the screen aspect ratio (that is, width to height) from the current 12:9 to 16:9, which would create a television screen shaped more like a movie screen.
HID specification The device class definition developed by the USB standards group for Human Interface Devices. Serves as the basis for WDM input device support, and unifies input devices by providing flexible data reporting, typeless data, and arrayed and variable input and output.