In computing, a hardware register is a storage area for hardware I/O (input/output) of different kinds. The hardware register is contained within a certain peripheral unit, and presented to the central processing unit of the computer by means of memory-mapped I/O or port-mapped I/O.

Typical uses of hardware registers include configuration and start-up of certain features, especially during initialization, buffer storage e.g. video memory for graphics cards, and status reporting such as whether a certain event has occurred in the hardware unit.

Reading a hardware register involves accessing its memory- or port-address with a "load" or "store" instruction, issued by the processor. Hardware registers are addressed in words, but sometimes only use a few bits of the word read in to, or written out to the register.

See also

• Register Transfer Language