Meaning – A controller is a device that coordinates and controls the operation of one or more input/output devices, such as workstations, and synchronises the operation of such devices with the operation of the system as a whole.
A controller can also be defined as an integrated circuit on the computermotherboard that enables communication between the computer and another hardware device.
A controller can also be referred to mean the joystick that is used as an input device in gaming consoles.
When we talk about larger devices like mainframe computers, a controller is referred as either a separate device attached to a channel or integrated into the peripheral.
Example of usage – “Common devices that are classified as controllers include AGP, PCI cards, SATA, USB devices, etc.”