Overview Of PC

The Complete PC (Personal Computer)

Most computers have a standard set of peripherals to provide input and output.

• Monitor The big television thing that provides a visual output for the computer.

• Keyboard Keypad for providing keyed input. Based on a typewriter.

• Mouse Pointing device used to control a graphical pointer on the monitor for input.

• Speakers/headphone Speakers provide sound output.

• Printer Provides printed paper output.

A typical PC has all of these peripherals, but there’s no law that requires a PC to have them. Plenty of PCs may not have a printer. Some PCs won’t have speakers. Some computers don’t even have a keyboard, mouse, or monitor—but they tend to hide in unlikely places, such as the inside of a jet fighter or next to the engine in an automobile. Other PCs may have many more peripherals. It’s easy to install four or five printers on a single PC if you so desire. There are also hundreds of other types of peripherals, such as Web cameras and microphones, that you’ll find on many PCs. You add or remove peripherals depending on what you need from the system.

CPU

The central processing unit (CPU), also called the microprocessor, performs all the calculations that take place inside a PC. CPUs come in a variety of shapes and sizes, as shown in Figure

Modern CPUs generate a lot of heat and thus require a cooling fan and heat sink assembly to avoid overheating . A heat sink is a big slab of copper or aluminum that helps draw heat away from the processor. The fan then blows the heat out into the case. You can usually remove this cooling device if you need to replace it, although some CPU manufacturers have sold CPUs with a fan permanently attached.

RAM

Random access memory (RAM) stores programs and data currently being used by the CPU. The maximum amount of programs and data that a piece of RAM can store is measured in units called bytes. Modern PCs have many millions, even billions, of bytes of RAM, so RAM is measured in units called megabytes (MB) or gigabytes (GB). An average PC will have from 256 MB to 2 GB of RAM, although you may see PCs with far more or far less RAM. Each piece of RAM is called a stick. One common type of stick found in today’s PC is called a dual inline memory module (DIMM)

Motherboard

You can compare a motherboard to the chassis of an automobile. In a car, everything connects to the chassis either directly or indirectly. In a PC, everything connects to the motherboard either directly or indirectly. A motherboard is a thin, flat piece of circuit board, usually green or gold, and often slightly larger than a typical piece of notebook paper

A motherboard contains a number of special sockets that accept various PC components. The CPU and RAM, for example, plug directly into the motherboard. Other devices, such as floppy drives, hard drives, CD and DVD drives, connect to the motherboard sockets through short cables. Motherboards also provide onboard connectors for external devices such as mice, printers, joysticks, and keyboards. All motherboards use multipurpose expansion slots that enable you to add adapter cards. Different types of expansion slots exist for different types of cards

Power Supply

The power supply, as its name implies, provides the necessary electrical power to make the PC operate. The power supply takes standard (in the United States) 110-volt AC power and converts it into 12-volt, 5-volt, and 3.3-volt DC power. Most power supplies are about the size of a shoebox cut in half and are usually a gray or metallic color

A number of connectors lead out of the power supply. Every power supply provides special connectors to power the motherboard and a number of other general-use connectors that provide power to any device that needs electricity.

Modem

A modem enables you to connect your PC to a telephone. A modem is another easily identifiable device in PCs. Most modems have two RJ-11 sockets. One connects the modem to the telephone jack on the wall, and the other is for an optional telephone so that you can use the phone line when the modem is not in use.

External modems traditionally connected to a male 9-pin or 25-pin D-subminiature port on the system unit called a serial port. Although just about every external modem today connects to USB, most computers come with a serial port for legacy devices. Serial ports are one of the few connectors on modern systems that were also used in the first PCs more than 20 years ago

Network

Networks are groups of connected PCs that share information. The PCs most commonly connect via some type of cabling that usually looks like an extra-think phone cable. A modern PC uses an RJ-45 connection to connect to the network. shows a typical RJ-45 network connector. Network connectors do not have a standard color.

Sound

The sound device on your card performs two functions. First, it takes digital information and turns it into sound, outputting the sound through speakers. Second, it takes sound that is input through a microphone and turns it into digital data. To play and record sounds, your sound device needs to connect to at least a set of speakers and a microphone. All PCs have at least two miniature audio jacks: one for a microphone and another for stereo speakers. Better cards provide extra miniature audio jacks for surround sound. A few sound cards provide a female 15-pin DB port that enables you to attach an electronic musical instrument interface or add a joystick to your PC.

VGA CARD

A monitor connects to the video connector on the system unit. You’ll usually see one of two types of video connectors: the older 15-pin female DB video graphics array (VGA) connector or the unique digital video interface (DVI) connector. VGA connectors are colored blue, whereas DVI connectors are white.

External Connections

Every peripheral connects to the system unit through one of the many types of ports. The back of a typical system unit has lots of cables running from the system unit to the different peripherals. You may even have a few connectors in the front. All these connectors and ports have their own naming conventions, and a good tech knows all of them. It’s not acceptable to go around saying things like “that’s a printer port” or “that’s a little-type keyboard connector.” You need to be comfortable with the more commonly used naming conventions so you can say “that’s a female DB-25” or “that’s a USB connector.”

Plugs, Ports, Jacks, and Connectors

Although PCs use close to 50 different types of connections, almost all fit into one of six major types: DIN, USB, FireWire, DB, RJ, and audio. Read the next paragraph to get your terminology straight, and then you can jump into the various connectors with gusto. No one seems to use the terms plug, port, jack, or connector correctly, so let’s get this right from the start. To connect one device to another, you need a cable containing the wires that make the connection. On each device, as well as on each end of the connecting cable, you need standardized parts to make that connection. Because these are usually electrical connections, you need one part to fit inside another to make a snug, safe connection.

A plug is a part with some type of projection that goes into a port. A port is a part that has some type of matching hole or slot that accepts the plug. You never put a port into a plug; it’s always the other way around. The term jack is used as an alternative to port, so you may also put a plug into a jack. The term connector describes either a port or a plug. As you progress through this chapter and see the different plugs and ports, this will become clearer.

Mini-DIN Connectors

Most PCs sport the European-designed mini-DIN connectors. The original DIN connector was replaced by mini-DIN a long time ago, so you’ll only see mini-DIN connectors on your PC .Older-style keyboards and mice plug into mini-DIN ports.

USB Connectors

Universal serial bus (USB) provides the most common general-purpose connection for PCs. You’ll find USB versions of many different devices, such as mice, keyboards, scanners, cameras, and printers. USB connections come in three different sizes: A (very common), B, and mini-B (less common). The USB A connector’s distinctive rectangular shape makes it easily recognizable

You never see a USB B connector on your computer. USB B connectors are for the other end of the USB cable where it attaches to the USB device

The USB B connector’s relatively large size makes it less than optimal for small devices such as cameras, so the USB folks also make the smaller mini-B–style connector

FireWire Connectors

FireWire, also known as IEEE 1394, moves data at incredibly high speeds, making it the perfect connection for highly specialized applications, such as streaming video from a digital video camera onto a hard drive. FireWire consists of a special 6-wire connector, as shown in Figure 2-18. There’s also a smaller, 4-pin version, usually seen on peripherals. Like USB, FireWire devices are hot-swappable.

DB Connectors

Over the years, DB connectors have been used for almost any type of peripheral you can think of, with the exception of keyboards. They have a slight D shape, which allows only one proper way to insert a plug into the socket and makes it easier to remember what they’re called. Technically, they’re known as D-sub or D-subminiature connectors, but most techs call them DB. Each male DB plug has a group of small pins that connect to DB ports. Female DB plugs connect to male DB ports on the system unit. DB connectors in the PC world can have from 9 to 37 pins or sockets, although you rarely see a DB connector with more than 25 pins or sockets. DB-type connectors are some of the oldest and most common connectors used in the back of PCs.

RJ Connectors

You have more than likely seen an RJ connector, whether or not you knew it by that name. The little plastic plug used to connect your telephone cord to the jack (techs don’t use the word “port” to describe RJ connectors) is a classic example of an RJ plug. Modern PCs use only two types of RJ jacks: the RJ-11 and the RJ-45. The phone jack is an RJ-11. It is used almost exclusively for modems. The slightly wider RJ-45 jack is used for your network connection.

Audio Connectors

Speakers and microphones connect to audio jacks on the system unit. The most common type of sound connector in popular use is the mini-audio connector. These small connectors have been around for years; they’re just like the plug you use to insert headphones into an iPod or similar device. Traditionally, you’d find the audio jacks on the back of the PC, but many newer models sport front audio connections as well.