a) Single word of memory. Registers within the CPU are more readily accessible than external memory locations. Registers external to the CPU are simply a group of flip-flops. b) A memory storage location. Each can store the data for a complete switcher setup. c) In a VGA controller, these are the storage elements that contain data relating to the mode or configuration of the device, as opposed to the display memory, which contains the image. Traditionally, the registers are divided into six groups: General, Sequencer, CRT Controller, Graphics Controllers, Attribute, and Extensions. The registers are accessed by a number of addressing schemes, usually involving an index or address register and a data register.