The Parts of a ComputerComputers are made up of hardware and software.Hardwareconsists of the physical objects (devices) that make up a computer. These commonly include a monitor or VDU (Visual Display Unit); the keyboard; the mouse; and the computer itself (the box), that contains the CPU (Central Processing Unit) and one or more of a floppy disk drive, a hard disk, and a CD-ROM drive.Some hardware devices are called peripherals. A Peripheral can be defined as any device that is part of a computer but not part of its CPU (the CPU is discussed below). They include devices for entering data into the computer, devices for storing data and information, and devices to display and/or print data taken from the computer.Peripheral devices for entering data into the computer are called input devices.Peripheral devices for storing data and information are called secondary or external memory.Peripheral devices to display data taken from the computer are called output devices.Softwareconsists of all the programs you run on your computer.HardwareInside the boxThe box contains the electronic parts of the computer. These are usually found attached to the computers motherboard.One of the most important components of a computer is the power supply.The power supply is located securely inside the box. It takes the normal electricity supply (240V) and converts it to a voltage level that the computer can use internally.The box usually contains a hard disk, floppy disk drive and/or a CD-ROM drive. These are usually attached to the motherboard via cables.

ProcessorsThe processor or CPU (Central Processing Unit) plugs into the computers motherboard. It is usually what people refer to when they talk about the computers chip.The processor controls the operation of the computer. It does all arithmetic operations, collects data from the input devices, sends data to output devices, records what programs you are running and what you are doing in them etc.The main criteria for a processor is speed. The faster the processor, the more work it can do in a set time period (usually one second). The speed of a processor is measured in MegaHertz (MHz). This is a measure of how many things a computer can do in one second. The higher the megahertz, the more things a computer can do in a second.Intel InsideIntel is the name of a company that manufactures computer chips. One of these chips is a CPU. The CPU chips made by Intel are called Pentiums. These come in a variety of speeds. The sign "Intel Inside" on the front of a computer means that the CPU in the computer was made by Intel.Internal MemoryInternal memory is plugged into the computers motherboard. It consists of RAM and ROM.ROM stands for read only memory. Anything stored as ROM can not be altered. ROM is usually set by the manufacturer of the computer to contain the programs necessary to start the computer. Turning off the computer does not erase the contents of ROM.RAM stands for random access memory. It temporarily stores data and information and programs while you are working with them. Turning off the computer erases the RAM contents.As the computer runs a program, it stores the program in RAM. If the program is bigger than the RAM (as most are) it is stored in the RAM in sections. The first section is put into RAM and run through, then the second section is read into RAM and run through, and so on. The more RAM a computer has, the bigger the section of the program it can store at one time. This means that the computer has to do less copying of sections.For example, you need 32M of RAM to run Windows 95 smoothly.Virtual memory is a way of making the computer operate as though it has more RAM than it actually does.MotherboardsA motherboard (called the main board in Apple Macintoshes) is a circuit board that has slots on it where components can be slotted into. Usually, the CPU and internal RAM and ROM are slotted onto the motherboard.The hard disk, floppy disk drive, and printer all connect directly to the motherboard via ribbon cables. When you plug your printer into the printer port at the back of the computer, it can connect to a cable that is connected to the motherboard. The keyboard and monitor connect directly to the motherboard.An example of a Motherboard.

TowersA Tower is a vertical computer box. More precisely it is an empty case that can be filled with components to make a computer. The power supply is the essential item, and most towers also contain a motherboard, internal and external memory.Towers come in different sizes. You can have a small, midi or full tower.Input DevicesCommon input devices are the keyboard, the mouse, the joystick, the trackball and the scanner. Disk drives are input, memory and output devices.The KeyboardThis is what you use to type information into your computer. It is the most common input device. Keyboards usually have a Qwerty layout.

Different keys on the keyboard have different names. They are used to do different things.Function keys perform a specific task. This task is set by the program you are using. For example, pressing F1 usually displays the help screen.Special purpose keys perform special preset tasks. For example, in Word 97 pressing the Print Scrn (Print Screen) key transfers a picture of your screen to the clipboard.The typewriter keys are used for typing text. They can also be used to perform tasks that appear on the programs menus. For example, in Word 97, Ctrl+V (hold down the control and the V key at the same time) does the same action as Edit / Paste (select Paste from the Edit menu).Pressing TAB moves you to the next tab in a word processing program and the next cell in a spreadsheet program.Caps Lock sets to capitals all the text you write.The Enter key causes data to be accepted by the computer. If you are typing, pressing the enter key begins a new paragraph.The cursor control keys move your cursor (the flashing bar where text appears) around the screen.Numeric keys allow you to enter numbers quickly.The MouseThis is another common input device. A mouse is used to point to information on the screen and either Click on it or Click and drag the information.A Mouse can have one, two or three buttons.On a two button mouse:ToClickmeans to quickly press down and release the left mouse button.ToDouble Clickmeans to give two clicks very quickly, one after the other.ToRight Clickmeans to click with the right mouse button. This will perform a different action to normal clicking (done with the left mouse button).ToClick and Dragmeans to point the mouse at an object, hold down the left mouse button, move the mouse, and release the left mouse button. This moves the object you pointed to from where it was to where it is when you release the mouse button.The JoystickThese are used mainly in computer games. Moving the joystick will move the car / person / object on the screen.The TrackballA trackball has been described as an upside down mouse. It is a small ball with buttons around it that is either part of the keyboard or attached to the keyboard. Moving the ball moves the pointer on the computer screen. The buttons are used to do the same things as the buttons on a mouse. A trackball is used instead of a mouse in notebook and laptop computers.The ScannerThis is used to put both text (writing) and graphics (pictures) into the computer. It digitises the text and images i.e. it converts them into a form that can be used in the computer. This process is known as optical character recognition (O.C.R). Before the text can be used on the computer, it has to be converted into characters by optical recognition software.Output DevicesThe MonitorThis is the most commonly used output device. It displays what you have typed or otherwise entered in to the computer on the screen in front of you.Monitors can be monochrome (black and white, black and green or black and amber), or colour.Colour monitors come in various types. Each type has a different number of colours to use and a different quality of picture (resolution). The higher the resolution, the better the quality of the pictures on the screen.Resolution is measured in pixels. The screen is divided into a grid. Each square on the grid is a pixel. The more pixels are on the screen, the more detail can be shown in the pictures on the screen and the higher the resolution of the screen is.CGA (Colour Graphics Adapter). These monitors have 4 colours and a very low resolution (320x200 pixels).EGA (Enhanced Graphics Adapter). These monitors have 16 colours and a low resolution (640x350 pixels).VGA (Video Graphics Array). These monitors come in two types. One is similar to the EGA monitor. It has 16 colours and a resolution of 640x4800 pixels). The other one has 256 colours and a lower resolution (320x200 pixels).Super VGA. These monitors have very high resolution. They come in two types. Both types have 256 colours. One has a resolution of 800x600 pixels, the other of 1024x768 pixels. You can run the Super VGA monitor as a VGA monitor. This speeds up the time it takes the screen to display things as there are not so many pixels to be coloured in.XGA (Extended Graphics Array). These monitors have 1024x768 pixels. It normally has 256 colours. With special equipment it can show up to 65,536 colours.Most people will use a VGA or Super VGA monitor.The PrinterThis is the other common output device. It prints information and data from the computer on to paper. There are different types of printers.ADot Matrixprinter is an impact printer that forms characters as a series of dots. The print head contains a grid of pins which form a character. This heads stamps on to the paper through an inked ribbon to produce a character (for example, "H") that is made up of dots.The print heads can have from 9 to 24 pins in them. The more pins the print head has, the better the quality of the printed output. Printers with 24 pins produce letter quality output.The quality of the printed output is measured in dpi (dots per inch). The higher the dpi, the better the quality of the printed output.Dot Matrix printers come with a standard parallel interface. They can also use a serial interface. Parallel interfaces are faster, but serial interfaces can be used over greater distances.Impact printers are the only printers that will make an impression on carbon paper. Any printing that is done on paper with a carbon behind it or on self carbonated paper needs to be done on an impact printer for the printing come through on the second layer of paper.AnInk Jetprinter prints characters by spraying very fine jets of ink on to the paper. It works best with non-absorbent paper.ABubble Jetprinter vaporizes part of the ink. The bubble that is created puts ink onto the page.ALaserprinter uses a laser beam to print. The laser creates an image on a drum inside the printer. This picks up toner and prints the image on to the paper like a photocopier does.How Dot Matrix Printer Works.

How Laser Printer Works.

STORAGEThere are lots of ways you can store an electronic (soft) copy of your files. The major storage devices available are: Tape, 3.5 inch Floppy Disk, Hard Disk, CD-ROM disk, CD-ROM write disk, Zipp disks, Jaz disks, and Flopticals. The newest technology is DVD disks.TapeData and information is stored on a magnetic tape. These look like small cassette tapes. The major disadvantage if tape storage is that it is sequential. Every time you want to find something on the tape, the computer has to start at the beginning of the tape to search for it.All other methods of storing data and information are random access. The computer finds out where the information is and goes directly to that location.Floppy DisksA floppy disk is one that you put in a disk drive. The ones available today are 3.5 inches wide and have a hard plastic cover.Inside the disk is a circle of magnetic material (like what is in a cassette tape).The silver bits protect this magnetic material. To read or save something on your disk, the disk drive pushes back the silver square at the top of the disk. A head (it looks like a toothbrush) extends over the square in the protective casing that the silver bit usually covers. The magnetic disk inside the casing spins rapidly. The required data or information is read by the disk drive head from the magnetic disk.DO NOT PLAY WITH THE SILVER BITS ON YOUR DISK.If they are fiddled with, the spring inside the silver bits can come loose. Then the silver cover may break off and could even lodge in your disk drive. You will not be able to use that disk any more.Moving the silver bits increases the risk of dust making its way inside the protective casing and on to the magnetic disk. Where ever the dust settles, you will not be able to use that part of the magnetic disk.How a Disk Drive Works.

Things that can cause a Disk Drive to not work.

Care of Floppy DisksDo not bend the disk.Do not put heavy weights on the disk.Do not write on the disk with sharp objects.Do not touch anything visible inside the protective cover.Do not expose disks to strong magnetic fields.Do not expose disks to extreme heat.Do not expose disks to chemicals.Hard Disks

A hard disk is usually inside the computer. It is a rigid metal disk which is covered in magnetic material. It is read the same way as a floppy disk. Hard disks can spin much faster than floppy disks, which makes retrieving information and data from them a lot quicker. Because it is in a sealed environment, and because it is of metal, information and data can be stored more densely on a hard disk than on a floppy disk.CD-ROMCD-ROMs work very differently. The name is an acronym for Compact Disk - Read Only Memory. You cannot save information or data to a CD-ROM using a normal CD-ROM drive. The information or data on CD-ROMs is recorded on it by the manufacturer.A CD-ROM stores information and data using light beams. The data is burned into the disk on a spiral track as a series of pits and islands. A coloured laser beam reflecting off this track reads the data and information on the disk.Some CD-ROMs are writeable. You can save information to these disks. They can be used only once.How a CD-ROM Drive Works

zipp DisksZipp disks are approximately 3.5 (9 cm) inches wide. They are thicker than floppy disks.Zipp disks store data and information in a similar way to floppy disks. They hold 100 Mb. They need to be formatted before use.Jaz DisksJaz disks are approximately 3.5 inches (9 cm) wide. Jaz disks are thicker than Zipp disks (about 1 cm thick).A Jaz disk works like a hard disk does. They holds 1 Gb. They need to be formatted before use.FlopticalsA floptical is a floppy disk that stores information using optical technology. It looks like a floppy disk.DVD-ROMDVD-ROM disks are the newest technology. They look like a CD-ROM and store data and information in a similar way (using pits and islands). They cannot be formatted and have a far greater storage capacity than CD-ROMs. One single sided DVD-Rom holds 4.7 Gb. In the future, double sided double layer platters will hold 17 Gb per disk.