GCSE ICT Revision - Hardware - RevisionWorld.com

Digital versatile disk (DVD)

A DVD disc can store up to 17 gigabytes of data. This is enough storage space for at least four full-length feature films!

Concept Keyboard

A concept keyboard is a flat board with a grid of programmable keys on its surface. A single key or a group of keys can be set up to carry out a particular task. Paper overlays are placed on top of the keyboard with pictures drawn on them. Concept keyboards are often used with young children in primary schools who can't use an ordinary keyboard very well.

Digital Camera

A digital camera can store many more pictures than an ordinary camera. Pictures taken using a digital camera are stored inside its memory and can be transferred to a computer by connecting the camera to it. A digital camera takes pictures by converting the light passing through the lens at the front into a digital image.

Dot Matrix Printers

A dot matrix printer forms characters and graphics on the paper by producing patterns of dots. If you look closely at a print-out from a dot matrix printer you will see the tiny dots which make up the printout.

Floppy Disks

A floppy disk a circular piece of plastic coated with a magnetic material and protected by a hard plastic cover. The formatting process involves dividing the surface of the disk into invisible circles called tracks and sectors, setting up a root directory where the list of files that are on the disk will be kept.

Graphics Tablet

A graphics tablet consists of a flat surface and a pen, or stylus, which can be used to produce freehand drawings or trace around shapes. When the special pen touches the surface of the graphics tablet data about its position is sent to the computer.

Hard Disk Drives

A hard disk is a circular metal disk coated with magnetic material and usually sealed in a hard disk drive inside the computer. Some hard disk drives are not permanently fixed inside the computer but are removable. Data stored on a hard disk can be accessed much more quickly than data stored on a floppy disk. Hard disks can store much more data than a floppy disk. A typical hard disk inside a personal computer can hold several gigabytes of data.

Light Pen

A light pen is a small 'pen-shaped' wand, which contains light sensors. It is used to choose objects or commands on the screen either by pressing it against the surface of the screen or by pressing a small switch on its side.

Microphone

A microphone is used to input sound into a computer system. Microphones are often used for voice recognition systems which convert sounds made by a user into commands that the computer can carry out. As computers become more powerful in the future, voice recognition will be a much more common input method for all computer users.

Monitor

A monitor or screen is an output device that can display graphics and text and video. The picture on a monitor is made up of thousands of tiny coloured dots called pixels. The quality of the output on a monitor depends on its resolution.

Pointing devices

A mouse is a pointing device. It is the next most common type of input device after the keyboard. Touch pads and trackballs are also types of pointing device. They are often used instead of a mouse on portable computers.

Scanner

A scanner can be used to input pictures and text into a computer. There are two main types of scanner; Hand-held and Flat-bed.

Touch screen

A touch screen can detect exactly where on its surface it has been touched. Touch screens are used in a lot of fast food chains and restaurants because they are easy to keep clean and re-program if changes need to be made to the menu.

Backing storage

Backing storage is used to store programs and data when they are not being used or when a computer is switched off. When programs and data are needed they are copied into main memory but also still remain on backing storage. Magnetic tape drives, floppy disk drives and hard disk drives are all examples of backing storage devices.

Output Peripherals, or Devices

Before any output can be produced by a computer it must have an output device connected to it. The output devices that you are probably most used to will be the screen, or monitor, and the printer. Another sort of output that you will have experienced when using a computer is sound, which is output through a speaker.

CD-ROM

CD-ROM stands for compact disk read only memory. CD-ROMs can store approximately 650 megabytes of data which is four hundred times more data than an ordinary 3½ inch floppy disk. CD-ROM disks come with information already on them and are read only. This means that the information on a CD-ROM cannot be erased or changed, and no new information can be saved.

Speakers

Computers can output music, voices and many other complicated sounds using speakers. To be able to output sound a computer needs to have a special circuit board inside it called a sound card.

Storing Data, Devices and Media

Data storage devices can be divided into 2 main categories: Backing storage and Main Memory.

File Compression

File compression software can be used to make files smaller so that more data can be stored in the same amount of space on backing store. When a compressed file on backing store needs to be used it must be decompressed. This can be done using decompression software or by setting files up to be self-extracting which means that they can automatically decompress themselves, e.g. Winzip

Direct and serial access

Floppy disks, hard disks and CDs all allow direct access to data. Direct access means that the required data can be found straight away without having to read through all the data on the disk. Magnetic tape allows only serial access to data. To locate data on a magnetic tape it has to be searched from the beginning until the required data is found.

Inkjet Printers

Inkjet printers work like dot matrix printers because the printouts that they produce are made up of patterns of very small dots but the print head has a set of tiny holes rather than pins. As the print head moves across the paper ink is forced out through the holes to form the image. Inkjet printers are very quiet to operate and can produce good-quality printouts of both graphics and text. Relatively cheap colour graphics can be printed using a colour inkjet.

Laser Printers

Laser printers give very high-quality printed output of both text and graphics very quickly and quietly. They are generally more expensive to buy than inkjet printers and the toner cartridges are more expensive. They are very suitable for large volume printouts because of their speed.

Magnetic Tape

Magnetic tape comes in two forms; tape reels, and cassettes or cartridges. Large tape reels are used to make backup copies of programs and data on large mainframe computers. Cartridges are used to make backup copies of the programs and data on personal computers and networks. The main advantage of using magnetic tape as backing storage is that it is relatively cheap and can store large amounts of data.

Manual Input Peripherals, or Devices

Manual input devices are used by people to enter data by hand.

PROM and EPROM

PROM and EPROM are both special types of programmable read only memory. PROM stands for Programmable Read Only Memory. This type of memory can be programmed once but can't be changed again afterwards. EPROM stands for Erasable Programmable Read Only Memory. This type of memory can be programmed and then changed whenever necessary.

Random Access Memory (RAM)

RAM is the computer's 'working memory'. RAM temporarily stores programs and data that are being used at a given time. The contents of RAM can be changed and are lost when the computer is turned off. Memory which is wiped clean when the computer is turned off is called volatile memory.

Main Memory

The Main Memory contains two types of memory chip called ROM and RAM which hold program instructions and data.

Keyboard

The keyboard is the most common type of input device. Ordinary computer keyboards have their keys arranged in a similar way to those on a typewriter.

Plotters

The main difference between a plotter and a printer is that a plotter uses a pen to draw the computer output onto the paper. Plotters produce very accurate drawings and are often used in computer aided design or CAD.

Read Only Memory (ROM)

The main use of ROM memory chips in a computer is to store the program that runs when the computer is turned on which loads the operating system (e.g. Windows 8) from disk. The contents of ROM can't be changed and aren't lost when the computer is switched off. Memory which isn't wiped clean when the computer is turned off is called non-volatile memory.

Joystick

The main use of a joystick is to play computer games by controlling the way that something moves on the screen. A joystick will also always have at least one button on it which can be used to make something happen like making a character in a game jump or fire a gun.

Writeable CD's

Writeable compact disks are supplied blank and can have data put onto them using a special read/write CD drive. There are two main types of writeable compact disk: WORM (Write-Once, Read-Many) disks which can have data written to them just once or Magneto-Optical disks which can have data written to them any number of times just like a hard disk.