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A Human Interface Device (HID) is a variety of computer add-on designed to be used directly by people. Unlike other devices such as external hard drives or wireless cards, HIDs typically feature buttons or controls that allow humans to interact with the computer. The majority of modern Human Interface Devices use the Universal Serial Bus (USB) communication protocol; the term HID usually refers to this device type.
The designation “Human Interface Device” was created by engineers working at Microsoft™ Corporation in the late 1990s. Before this time, the number of protocols for computer devices was limited. Manufacturers were restricted to creating input devices that fell into narrow categories, such as joysticks or keyboards. Computer companies were forced to write completely new device instructions called “drivers” any time a new experimental input controller was made.
A Human Interface Device hardware classification was designed to address this limitation and encourage new types of input devices to be built. If a manufacturer follows the HID hardware guidelines, they can safely assume that their product will work properly with most modern computers. The majority of operating systems in use, including both Windows and Mac platforms, support the Human Interface Device specifications.
HIDs contain pre-programmed data, called “HID descriptors,” that is reported to a host computer when the device is first connected. The HID descriptors tell the computer the purpose of each packet of information that will be sent from the interface device. Essentially, this data provides an “update” to the host and notifies the computer of which inputs to expect.
While most HID hardware is designed for users to control the computer, the protocol is not limited to only inputs. HID outputs can also be sent from the computer to a device. This communication capability is often used to provide information, such as status lights. Some devices use the output capability to help immerse a user into a program or game through vibration or force-feedback.
Most Human Interface Devices are “plug and play” compatible, which means that they can be connected and used almost immediately. A plug and play HID controller does not need the computer to reset before it can be used, and does not require the user to load external drivers. These features can save time and minimize installation hassles.
The use of HID specifications has allowed manufacturers to create a wide variety of different interface controls, all using the same general drivers. In addition to standard keyboards and mice, many video game controllers use this protocol. Other examples of Human Interface Devices include dance pads, vehicle simulation controls, exercise machines, and hospital medical instruments.