The two pictures below are two typical PCs, taken from the Onlinehelp offices. To state the obvious, these two PCs are different - the cases are different, and the sockets are in a different place. We did this to show you that there are so many different combinations of PC, so what you may see on one PC may well be in a different place on your own. However, the sockets themselves are always the same - an AT-Style Keyboard socket is always the same shape and size, as is a nine-pin serial socket (COM port). If you are learning about the back of a PC for the first time, try to remember what the sockets look like, rather than where they are on the back of the machine. Click the images to see the full size version.

The Power Supply Cooling Fan is there because the power supply works very hard giving all the hardware components power. Without it, the power supply would overheat and possibly catch fire! The Pass Through Connector is a socket which allows you to pass power through to the monitor. This is particularly useful if you are limited on power outlets on a wall socket or extension lead. The Power Connector is where the power actually comes into the PC, from a wall socket or extension lead.

The small COM Port (also known as a serial port) is usually used for attaching a mouse, modem or digital camera. The large COM Port, usually connected as "COM2" is primarily used for attaching a modem with the bigger connector. The Parallel Port (also known as the printer port or LPT1) is mainly for attaching a printer to your system. However, sometimes it can be used for external devices such as scanners or CD-Rom drives. The AT-Style Keyboard Connector is only used to connect a keyboard with a large AT-Style connector.

The Modem Expansion Card removes the need to have an external modem attached via a COM Port. It is an expansion card, so it fits into an expansion slot inside the PC, and the phone lines plug into the back of it.

Graphics Cards are essential for a PC: even though a PC might only be displaying text, the image is still created by the graphics card, so without one a PC is unuseable. Graphics Cards tend to only have one connector on the back, which is where a monitor plugs into. They tend to come in either of two configurations - as an expansion card (like this one), or directly on the motherboard. The configuration that they come in has a large bearing on where the socket for the monitor is actually located.

Network Cards are not normally included as standard in a PC, and are only of use in a corporate environment or in a multi-computer environment where network games are to be played. Like the graphics card, they can either come as an expansion card (like the one here), or directly on the motherboard.

Sound Cards are usually standard equipment in modern PCs with the revolution of multimedia and the Internet, as well as games. These cards create the sound and music that can be heard through the speakers, and normally the sound from a music CD comes through the sound card as well (the CD-Rom drive and the sound card are connected Internally)

MPEG Cards allow computers to play MPEG movie files, such as DVD, without any jerkiness or obvious errors. Many newer PCs will play DVD without an MPEG Card, but the quality is much higher when using a card. The card also has sound outputs, to connect to a stereo system for surround sound.

PS/2 Keyboard and Mouse Connectors are a different standard for connecting these devices to a PC. PS/2 Mouse connectors are especially good as they don't use a serial port, freeing it up for a modem or digital camera for example.

Yamaha XG Synthesizer is an additional card to a standard sound card, with studio-quality MIDI sounds for writing music. Only really to be used by the avid composer, as most users won't utilise the benefits of a card such as this.