A device controller is an entity in a computer that is primarily responsible for controlling one or more I/O devices to facilitate data exchange between the I/O devices and the computer. It is the interface between the CPU and I/O devices, which receives commands from the CPU and controls the operation of I/O devices, freeing the processor from complex device control transactions. A device controller is an addressable device that has only one unique device address when it controls only one device; If the control can connect multiple devices, it should contain multiple device addresses and correspond to each device address. The complexity of device controllers varies greatly among different devices, so device controllers can be divided into two categories: one is used to control character devices, and the other is used to control block devices. The controller in microcomputers and mini computers is often made in the form of a printed circuit card, and is therefore also commonly referred to as an interface card, which can be inserted into a computer. Some controllers can also handle two, four, or eight similar devices.
