The Central Processing Unit The CPU (Central Processing Unit) is the processor within the
It is a microchip which carries out all of the searching, sorting,
selecting and calculating within the computer.
The CPU also has an internal clock which determines the maximum speed
at which everything within the computer is done.
CPUs run at different speeds measured in MHz.
The Intel Pentium 4 shown above runs at a maximum of 2.2GHz.
The most common CPUs in PCs are Celeron Processors and Pentium
Processors both made by Intel.
The CPU is plugged into the motherboard enabling it fast access to all
devices especially ROM and RAM chips.
Main Processing Unit Devices - Motherboard
The Motherboard is the heart of the computer, into which everything
When you buy a computer it usually has a Motherboard which already has
a CPU, RAM, ROM, Ports and Connecting leads. The Hard Disk Drive and
Floppy Disk Drive are connected directly to the Motherboard.
Usually there are also a number of spare slots to attach additional
devices such as RAM, Sound Cards etc.
These spaces are known as expansion slots.
An advantage of Motherboards is that they make it easier to upgrade an
existing computer rather than buying a whole new PC.
Main Processing Unit Devices - Ports
A port is a point at which you can attach leads from devices to the
Main Processing Unit.
Ports can be at the front or the back of a computer.
The ones in the picture are hidden by a flap at the front of the PC.
Ports are of different types and are of different shapes and sizes
A few examples are:
Common small round connector for a keyboard or mouse
A common small D shaped connector for serial devices
(some mice and keyboards connect in this way)
A longer but thin D shaped connector for parallel devices often used
for connecting a printer
A small socket usually labelled USB. A fast new alternative way to
connect to modern devices, such as USB Scanners, USB Joysticks, USB
Main Processing Unit Devices - Modem
Modems can be External (connected by a lead to a Port) or Internal
(fixed to a slot on the Motherboard)
A modem allows a computer to send and receive data through a telephone
Modems transmit data at different speeds known as Baud Rate.
Speed is measured in Bits per Second or bps.
It is common for modems in the home to transmit and receive data at 56
External modems are becoming less common because most new computers
come with an internal modem already fitted to the Motherboard.
Modems are a common way to connect to the Internet.
Other methods include Cable and ISDN,...