The controller involves two sides. One that controls called a controller, not an observer of events. Also it means an officer who accounts and supervises the financial affairs of a corporation of a government body. The other that a regulating mechanism, as in a vehicle or electric device.
Each set of the computer needs controllers. As you need to play video games, there is a device used to play it, of course a video game controller is necessary. Controller is a chip, an expansion card or a stand alone device that interfaces with a peripheral device in computing and in computer hardware especially. This perhaps is a link between two parts of a computer or a controller on an external device that manages the operation of that device. The term is used in the opposite sense to refer to a device by which the user controls the operation of the computer sometimes as in game controller. In desktop computers the controller may be a plug in board, a single integrated circuit on motherboard or an external device. In mainframes the controller is usually either a separate device attached to a channel or integrated into the peripheral.
Controller can be separated in several parts. The board controllers are graphics controller or video display controller, SCSI controller. The controller chips as chip densities improved controllers were implemented as single chips and often located on the motherboard. Printer Mechanism It including keyboard controller, programmable interrupt controller, Intel memory controller chip, Intel I/O controller chip, UART communications controller chip, memory controller, peripheral DMA controller and floppy disk controller. External controllers are disk controller, disk array controller, flash controller and terminal access controller. The disk controller often integrated into modern disk drives. The disk array controller is also known as RAIS controller is a type of shortage controller. Flash controller or SSD controller manages flash memory.