parts of computer.docx

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Parts of a computerIf you use a desktop computer, you might already know that there isn't any single part called the

"computer." A computer is really a system of many parts working together. The physical parts, whichyou can see and touch, are collectively called hardware. (Software, on the other hand, refers to the

instructions, or programs, that tell the hardware what to do.)

The illustration below shows the most common hardware in a desktop computer system. Your system

may look a little different, but it probably has most of these parts. A laptop computer has similar parts

but combines them into a single notebook-sized package.

Desktop computer system

System unit

The system unit is the core of a computer system. Usually it's a rectangular box placed on or

underneath your desk. Inside this box are many electronic components that process information. The

most important of these components is the central processing unit (CPU), or microprocessor, which

acts as the "brain" of your computer. Another component is random access memory (RAM), which

temporarily stores information that the CPU uses while the computer is on. The information stored in

RAM is erased when the computer is turned off.

Almost every other part of your computer connects to the system unit using cables. The cables plug

into specific ports(openings), typically on the back of the system unit. Hardware that is not part of the

system unit is sometimes called a peripheral device or device.



System unit

Storage

Your computer has one or more disk drives—devices that store information on a metal or plastic disk.

The disk preserves the information even when your computer is turned off.

Hard disk drive

Your computer's hard disk drive stores information on a hard disk , a rigid platter or stack of platters

with a magnetic surface. Because hard disks can hold massive amounts of information, they usuallyserve as your computer's primary means of storage, holding almost all of your programs and files. The

hard disk drive is normally located inside the system unit.

Hard disk drive

CD and DVD drives

Nearly all computers today come equipped with a CD or DVD drive, usually located on the front of the

system unit. CD drives use lasers to read (retrieve) data from a CD, and many CD drives can also write



(record) data onto CDs. If you have a recordable disk drive, you can store copies of your files on blank

CDs. You can also use a CD drive to play music CDs on your computer.

CD

DVD drives can do everything that CD drives can, plus read DVDs. If you have a DVD drive, you can

watch movies on your computer. Many DVD drives can record data onto blank DVDs.

If you have a recordable CD or DVD drive, periodically back up (copy) your important files to CDs or

DVDs. That way, if your hard disk ever fails, you won't lose your data.

Floppy disk drive

Floppy disk drives store information on floppy disks, also called floppies or diskettes. Compared to

CDs and DVDs, floppy disks can store only a small amount of data. They also retrieve information

more slowly and are more prone to damage. For these reasons, floppy disk drives are less popularthan they used to be, although some computers still include them.

Floppy disk

Why are floppy disks "floppy"? Even though the outside is made of hard plastic, that's just the sleeve.

The disk inside is made of a thin, flexible vinyl material.

Mouse

A mouse is a small device used to point to and select items on your computer screen. Although mice

come in many shapes, the typical mouse does look a bit like an actual mouse. It's small, oblong, and

connected to the system unit by a long wire that resembles a tail. Some newer mice are wireless.



Mouse

A mouse usually has two buttons: a primary button (usually the left button) and a secondary button.

Many mice also have a wheel between the two buttons, which allows you to scroll smoothly through

screens of information.

When you move the mouse with your hand, a pointer on your screen moves in the

same direction. (The pointer's appearance might change depending on where it's positioned on your

screen.) When you want to select an item, you point to the item and then click (press and release) the

primary button. Pointing and clicking with your mouse is the main way to interact with your computer.

For more information,

Keyboard

A keyboard is used mainly for typing text into your computer. Like the keyboard on a typewriter, it has

keys for letters and numbers, but it also has special keys:

The function keys, found on the top row, perform different functions depending on where they

are used.

The numeric keypad, located on the right side of most keyboards, allows you to enter numbers

quickly.

The navigation keys, such as the arrow keys, allow you to move your position within a

document or webpage.

Keyboard

You can also use your keyboard to perform many of the same tasks you can perform with a mouse.

For more information,



Monitor

A monitor displays information in visual form, using text and graphics. The portion of the monitor

that displays the information is called the screen. Like a television screen, a computer screen can show

still or moving pictures.

There are two basic types of monitors: CRT (cathode ray tube) monitors and LCD (liquid crystal

display) monitors. Both types produce sharp images, but LCD monitors have the advantage of being

much thinner and lighter. CRT monitors, however, are generally more affordable.

LCD monitor (left); CRT monitor (right)

Printer

A printer transfers data from a computer onto paper. You don't need a printer to use your computer,

but having one allows you to print e-mail, cards, invitations, announcements, and other materials.Many people also like being able to print their own photos at home.

The two main types of printers are inkjet printers and laser printers. Inkjet printers are the most

popular printers for the home. They can print in black and white or in full color and can produce high-

quality photographs when used with special paper. Laser printers are faster and generally better able

to handle heavy use.

Inkjet printer (left); laser printer (right)



Speakers

Speakers are used to play sound. They may be built into the system unit or connected with cables.

Speakers allow you to listen to music and hear sound effects from your computer.

Computer speakers

Modem

To connect your computer to the Internet, you need a modem. A modem is a device that sends and

receives computer information over a telephone line or high-speed cable. Modems are sometimes

built into the system unit, but higher-speed modems are usually separate components.

Cable modem

Main Parts Of A Computer

Processor (CPU) - The part of the computer that handles all processes

and instructions supplied by memory unit (RAM)

Memory (RAM) - Random Accessed Memory. The area of the computer that

holds the instructions (processes) and information system gives it.

When you turn the computer off, everything in RAM disappears.

Read Only Memory (ROM) - A chip or disk that holds information that

cannot be changed. Ex CD-ROM, DVD-ROM

Disk drive - A mechanical device that you use to transfer informationback and forth between the computer's memory and a disk.



Floppy disk (3.5") - A magnetically coated disk on which information

can be stored and retrieved. Capacity is 1.44MB - requires a

Floppy-Drive

Zip disk - A magnetically removable coated disk on which information

can be stored and retrieved. Capacity is 100 or 250MB or more -

requires a zip-drive

Hard disk - A large capacity storage area that offers access to store

and retrieve information, very slow compare to RAM.

Monitor - A screen that displays the information in the computer.

Keyboard - A device used to enter data and issue commands to the

computer.

Printer or Scanner - A devices that help to make hard copies o scan

documents into the computer.

Mouse - A small, hand-held device used to control the pointer on the

screen.

Software - Instructions that tell your computer how to perform a task.

Software is stored on the disks in program files. Software cannot be

seen or touched. There are two main kinds of software:

* application software and

* system software

Application software (program) - Software that does specific task,such as word processing. (Word, Power Point)

System software - Software that the computer system or OS operating

system.

Firmware - A kind of system software - instructions that are built

into the

computer system on ROM chips.

Operating System (OS) - software that acts as a link between you,

application software (programs), and hardware. (Windows 98, Mac OS 9,

Linux 7.2)

Graphical User Interface (GUI) - A phrase that is commonly used to

describe Microsoft Windows and other OS that use pictures to help you

communicate with the computer.

Inside the computer



I t may look l ike a co mpl icated mess of w ires, and

chips , but really it's quite simple.

The main parts of a computer Disks Drives

Disk drives provide a means of storing work, or data. Floppy disks are transportable from PC to PCand come in two sizes, 31/2" and 51/4" diameter.

Floppy disks provide a means of storing work. You can write information onto the diskand read information from the disk. Floppy disks are used by inserting them into a disk drive.

A light on the disk drive indicates when the disk is being accessed. Removing or inserting a diskwhile the drive light is illuminated may cause damage to the disk and is likely to result in theloss of data stored on the disk.

Hard disks are fixed inside the system unit and have much higher storage capacities than floppies.

Hard disks (or fixed disks) work on the same principle as floppy disks but are fixed inside the PC ina sealed unit. They can store a great deal more information than floppy disks and range in capacityfrom 10Mb to several hundred Mb. Access times (i.e. the time taken to read and write information)for hard disks are much faster than for floppy disks. Manufacturers often quote access times as wellas capacities for hard disks.

Information is stored on disk in the form of files. A file might be a program or data such as a wordprocessor document. Files can be grouped together on disk in directories.

Hard disks are contained in an air-sealed unit and are thus less liable to physical problems thanfloppies. However the consequences of any disk failure are much higher than for floppies so some

form of backup must be carried out regularly.



CD ROM Drives

Your computer may also have a CD player. As well as playing music, the CD- rom drive can readdigital information srtored on a computer CD. Today, many software programs come n CD insteadof floppy dosks. The programs for newer software applications are quite karge. These largeprograms, which may take as many as 20 floppy disks, can fit just fine on a single CD, which

reduces costs and makes installation much easier.

To distinguish them from music CD's the computer CD's are called CD-ROMS. This stands for Compact Disk-Read Only Memory.That is, a consumer is unable to erase or record information or programs onto a CD. If you want to advantage of recording, deleting and re-recording, then you usea a rewritable disk,(CR-RW).

Ports and Expansion Slots

Located at the rear of the PC are various sockets or ports. These allow the keyboard and monitor tobe connected. Most PCs include a parallel port (usually used for printers) and two serial ports(usually used for communications with other computer systems or connecting mice and plotters).

Also included inside the system box are expansion slots. These allow extra hardware to be addedto the PC using printed circuit boards, or cards, plugged into the expansion slots. The slots areconnected to the CPU via the bus. The bus is a set of wires which transfers data. Think of it as afreeway.

Motherboards. If the CPU is the brain of the computer, the motherboard and its components are the major systemsthis brain uses to control the rest of the computer. It is possibly the most important part of thecomputer. Having a good understanding of how the motherboard and its contained subsystemswork is probably the most critical part of getting a good understanding of how PCs work.

Here you can see the

connection from thepower supply to themotherboard. The power supply serves twofunctions. First of all itdraws power from theoutlet (usually 120V AC)and translates it intovoltages the computer can use (usually 12VDC). It also runs themain cooling fan whichprevents the computer

from overheating whichcan be detrimental to theintegrity of your data.

The motherboard is the

foundation of any PC. All

the critical subsystems,

including the CPU, the

system chipset, the

memory, the system I/O,

the expansion bus, and

other critical components

run directly off the

motherboard. Likewise, theinterconnections among



these components are built

into the motherboard itself.

It manages all transactions

of data between the CPU

and the peripherals. It

houses the CPU and its

second level cache, thechipset, the BIOS, the main

memory, the I/O chips, the

port for the keyboard, the

serial I/O, the parallel I/O,the disks, and the plug-in

cards.

Connections: Ports

Parallel - This port is commonly used to connect a printer.

Serial - This port is typically used to connect an external modem.

Universal Serial Bus (USB) - Quickly becoming the most popular external connection,USB ports offer power and versatility and are incredibly easy to use.

Firewire (IEEE 1394) - FireWire is a very popular method of connecting digital-videodevices, such as camcorders or digital recorders, to your computer.

Connections: Internet/Network

Modem - This is the standard method of connecting to the Internet..

Local Area Network LAN Card - This is used by many computers, particularly those inan Ethernet office network, to connected to each other.

Cable Modem - Some people now use the cable-television system in their home toconnect to the Internet.

Digital Subscriber Line DSL Modem. This is a high-speed connection that works over astandard telephone line.

Very high bit rate DSL (VDSL) - A newer variation of DSL, VDSL requires that your phoneline have fibre optic cables.

CLICK HERE for Power-up to Shut-down: BIOS

The Main Unit.

The main unit contains the Central Processing Unit (CPU) and various supporting IntegratedCircuits (or chips) all of which are fixed to a printed circuit board (PCB) called the motherboard . Themain unit also houses disk drives, expansion slots and the power supply.

The CPU

The CPU (Central Processing Unit) or processor is the `brain' of any computer system. In the PC itis contained on a single Integrated Circuit or `chip'. The CPU processes all instructions and data.

The CPU is driven by an internal clock. Simply speaking, every time the clock pulses the CPUprocesses one instruction. Thus, the faster the clock the quicker the CPU processes its instructions.Clock speed is measured in MegaHertz (MHz). All the real computing work is done by the CPU.

Memory.

All PCs are fitted with a certain amount of workspace memory called Random AccessMemory (RAM). This memory is used for storing running software and data which the software

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requires, as well as theoperating system. The contents of RAM are lost when the PC isswitched off . This in known as volitile because it is tempory in nature.For example, if you arerunning word processing software then the software and the document you are working on arestored in RAM. To save the document, after making any changes you wish to keep, it is necessaryto copy the document from RAM onto disk .

RAM chips can be individually installed directly on th motherboard or in the banks of several chipson a small board that plugs into the motherboard.The most common types of boards that holdmemory chips are called SIMMS (single inline memory modules), DIMMS (duel inline memorymodules), andRIMMS ( memory modules manufctured by Rambus,Inc.)

By contrast, another kind of memory holds its data permanently, even when the power is turned off.This type of memory is called non-volitile and is called ROM (read only memory).

ROM (Read-only Memory) contains the commands the computer needs to activate itself.Instructions in ROM let the computer start when the power is turned on, and, unlike RAM, itscontents are retained even when the power is off.

A Sound Card is an expansion card that lets a computer produce sound. Examples of practicaluses for sound capabilities include games, music applications, and interactive educational software.

The Expansion Card is a circuit board that slides into an expansion slot. It is used to addperipherals, such as a sound card or modem, to the PC.

An Expansion Slot is an opening on the motherboard into which a board or card can be inserting,expanding the capability of the computer.

The Power Supply is the vehicle through which electricity is regulated and sent to the various

components of a computer.

Components of a motherboard

Typical PC System Mainboard (Motherboard)

1. CPU Socket (for processor)2. CPU fan connector 3. ATX power supply connector (for plug from power supply in computer case)4. Memory Slots (for memory modules- new mainboards use DDR modules,previous generation uses SDRAM modules)5. Floppy Drive Connector (for data cable to floppy drive)6. Primary IDE Connector (data cable for hard drive, cd-drive - up to two devices)

7. Secondary IDE Connector (data cable for hard drive, cd-drive - up to twodevices)



8. Panel for connecting power switch, reset swtch, hard drive light, etc.9. CMOS Battery (keeps current BIOS Setup information intact)10. Chipset (contols specific functions)11. PCI Slots (for pugin cards such as modems, network cards, pci video cards,sound cards, etc.)

12. BIOS chip (see explanation below)13. AGP Slot (for Accelerated Graphics Port video card, today's standard)14. Chipset (controls specific functions)15. Connector for CDROM audio cable (for sound already built onto mainboard)16. On-board Audio Jacks (line in, line out, microphone jacks)17. Parallel Port & Serial Ports (parallel printer port plus one or two serial portswhich are hidden from view)18. USB Ports (new mainboards use USB 2.0, older use USB 1.1)19. Keyboard & Mouse Connectors (PS2 connectors, one for keyboard, one for mouse)

Many mainstream PC's today, especially lower priced ones, have the AGP Videocontroller, the Audio controller, Modem and NIC (Network Interface Card) built ontothe mainboard rather than on separate plug-in cards. On-board video uses aportion of the memory provided by the plug-in memory modules which is typicallyreserved for the rest of the system. This type of video does not perform well whenused for high-end graphics such as games.

It is possible that, even though the video chip is built on board, the manufacturer may have supplied an AGP slot so you can install your own Video card. Today'svideo cards contain at least 32mb of their own memory, and may go up to as highas 256mb. The on-board video would first need to be disabled in the BIOS/CMOSsetup routine before installing the card.

If the modem, sound, or network interface fail, or you want to upgrade them, theycan usually be disabled in the BIOS settings also, allowing for installation of a plug-in replacement card.

What is the BIOS or CMOS setup program? The motherboard contains a special chip called the BIOS, which is short for BasicInput/Output System. Burnt onto this chip are software instructions on how to load

basic computer hardware. Many PCs have what is called a flash BIOS, allowingthe user to update the BIOS if necessary. The BIOS also includes a sort of diagnostic routine known as the POST (Power On Self Test). This test ensures thatthe computer meets the necessary requirements to boot up correctly. If thecomputer doesn't pass the POST you will hear a pattern of beeps that indicate theproblem encountered.

CMOS (Complementary Metal Oxide Semiconductor) is a chip on the motherboardwhich stores system information and computer settings such as date, time, harddrive settings, boot sequence, parallel port settings, on-board audio & video,etc. This information can be accessed and changed through the BIOS/CMOSsetup program which is available as the computer begins to boot up. As the

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