Control
Control
units are in charge of the computer. Control units fetch and decode machine
instructions. Control units may also control some external devices.
A
bus is a set (group) of parallel lines that information (data,
addresses, instructions, and other information) travels on inside a computer.
Information travels on buses as a series of electrical pulses, each pulse
representing a one bit or a zero bit (there are trinary, or three-state, buses,
but they are rare). An internal bus is a bus inside the processor,
moving data, addresses, instructions, and other information between registers
and other internal components or units. An external bus is a bus outside
of the processor (but inside the computer), moving data, addresses, and other
information between major components (including cards) inside the computer.
Some common kinds of buses are the system bus, a data bus, an address bus, a
cache bus, a memory bus, and an I/O bus.