Information and Communication Technology
Hardware is the solid bits of the system, the things that you can actually touch. Hardware may be described as Input, Output, Storage, or Processing devices.
Software is the programs that are running on the computer, they are not objects that you touch, although you may be able to hold an item that stores them, e.g. a CD. Software may be described as Operating System or Application programs.
A bar code reader (or bar code scanner) is a device for reading printed bar codes. The device shines a light, usually from a Light Emitting Diode (LED) or a laser, onto the bar code and builds up an image from the reflections. Most barcode readers contain a decoding unit which converts the bar code's image into numbers and sends the data to the scanner's output port.
There are several different types of bar code scanner. Two common types are:
Stationary. These scanners are fixed to a wall or table and the bar code is passed over or beside them. They are often found at shop checkouts.
Handheld. Shown in the picture. These usually have a handle and a trigger button for operating the light source. They may also be pen or wand shaped. Handheld scanners may be used where a bar coded item is too big to be passed over a stationary scanner.
A chip reader is used to read information from a smart card.
A contact reader requires the smart card to be inserted into it so that electrical connections can be made with the contacts on the surface of the card. Cards that use the Chip and PIN system are read by contact readers. e.g. Credit and debit cards.
A contactless reader as shown in the picture, uses radio signals to read the card at a distance. Contactless readers are currently being used for reading items such as travel cards and driving licences and for collecting road tolls.
A digital camera is used to capture and store photographs
electronically instead of using photographic films like
Modern digital cameras are usually multifunctional, being able
to record sound and video as well as photographs. The pictures
can be downloaded to a computer. Some cameras allow the
pictures to be viewed by connecting to a television set.
The quality of the picture depends on the resolution of the
camera. Resolution is measured in megapixels.
One megapixel = 1,000,000 pixels.
Digital cameras are often included in other devices such
as mobile phones and PDAs.
Web Cams are digital cameras which are connected to a computer. They do not usually have any storage facility, each image being sent to the computer as it is taken. Web cams are often used for video conferencing.
A Graphics Tablet is a device that allows a user to hand-
Depending on the program used, the computer receives information about:
Graphics tablets are used for computer graphics and CAD. Small versions are often included in hand held devices for text input.
An inductance loop is a coil of wire which acts as a radio transmitter and receiver.
One use of an induction loop is to detect metal objects. As a metal object moves past the loop, an electric current is generated. Loops are often buried in the road at traffic lights as part of the traffic light control system.
A second use of an induction loop is in communications. Loops have been installed in buildings such as theatres and cinemas so a deaf person can have the sound transmitted to the processor in their hearing aid.
A joystick is a control device consisting of a handheld stick that pivots at one end and transmits its position to a computer. Most joysticks are two-
Joysticks are often used to control games. In addition to the stick movement, games joysticks usually have a set of buttons, switches and triggers whose state can be detected by the computer. These extra buttons, etc. can often be programmed to perform different functions for different games.
The Wii remote is an example of a joystick with real 3D motion and other controls as well.
Apart for controlling games, joysticks are also used for operating machines such as cranes, powered wheelchairs and remote controlled cameras and models.
A keyboard is designed for the input of text and characters,
and also to control the operation of a computer. A standard
computer keyboard is often called a QWERTY keyboard after
the first six keys on the top row of letters.
Most computer keyboards are rectangular, with rectangular
keys which have characters printed on them. Some keyboards
have a curved shape or are split into two halves. These are
attempts to make typing easier and avoid repetitive strain
In most cases, each press of a key corresponds to the symbol
shown on it. Some symbols require the user to press and hold
two or more keys at the same time, or in sequence.
e.g. Capital letters require SHIFT plus the letter. Other keys
do not produce a symbol, but affect the operation of the
computer or the keyboard instead, e.g. The Esc or function keys.
The effect of each key can be programmed so that keyboards
can be used for different languages.
A Concept Keyboard is a touch sensitive board that can be connected to a computer and used instead of the QWERTY keyboard. A thin overlay is placed onto the board, and the user presses symbols or pictures on the overlay. Some uses of concept keyboards are:
for disabled people who cannot operate a standard keyboard for young children who can press symbols or pictures rather than read or type for use in places where standard keyboards might get damaged. e.g. On public information boards or vending machines.
A keypad is a set of buttons, usually numeric, arranged in a block. Other symbols may be present but not a full set of letters. Keypads are found on the right hand side of most computer keyboards. They are also present on many other devices such as calculators, telephones and ATM machines.
A magnetic stripe reader is used to read the information on a magnetic stripe card. The magnetic stripe is read by swiping it past a reading head. Magnetic stripes are commonly used on credit cards, identity cards and train tickets.
Where the possibility of fraud is high, magnetic stripes are being phased out and replaced by smart cards, e.g. In credit cards.
A Magnetic Ink Character Reader is designed to read the numbers at the bottom of a typical cheque. The numbers are specially designed and are printed with magnetic ink. The result is that the error rate for scanning the numbers is smaller than with an Optical Character Reader (OCR) system.
The reader contains a device similar to the reading head of a tape recorder or magnetic stripe reader. It picks up the magnetic signature of the numbers and is not affected by them being written over in ordinary pen or pencil. The magnetic signature is converted to computer usable form by Magnetic Ink Character Recognition (MICR) software.
A microphone converts sound into an electrical signal which can be fed into a computer via a sound card.
The signal may be stored as a recording, using WAV, MP3 or other file formats for later playback. Alternatively the signal may be passed to a program which can detect speech or other noises.
Voice recognition software may be used to convert speech into text input or computer commands.
Security software may be used to detect sounds made by intruders.
Control software may be set to accept specific sounds as input for a control system.
A mouse is a handheld pointing device. It is designed to fit under the hand of a user and to detect movement made as it is moved over a surface. A mouse usually has two or more buttons and a wheel. These allow a user to perform various programmable operations such as scrolling or zooming. Extra buttons, wheels or switches can add more control functions.
The mouse's motion is usually used to control the movement of a pointer on a monitor.
Most mice are Ball or Optical.
A Ball mouse detects the movement of a ball held in a housing on
the bottom of the mouse. As the mouse is moved, the ball rolls
along the surface and, in turn, rotates two shafts. Movement of
one shaft is for the X axis and the other for the Y axis.
An Optical mouse uses a light beam and sensor to detect the
An optical scanner is a device that takes an object, such as a photograph or page of a book and produces a digital image of it. Most scanners are desktop (or flatbed) scanners.
A flatbed scanner has a glass panel under which there is a moving arm holding an array of optical sensors and a bright light. The object to be scanned is placed face down on the glass and the sensor array and light source move along the length of the scanner, reading the entire area.
The quality of the image depends on:
An Optical Character Reader is a scanner or digital camera with Optical Character Recognition (OCR) software and a microprocessor built in. It can convert typed and / or handwritten text into a computer usable format.
Optical Character Readers have been put into pen drives and mobile phones.
Most systems use a normal scanner or digital camera to form an image which is then sent to a computer running Optical Character Recognition (OCR) software.
An Optical Mark Reader is a scanner or digital camera with Optical Mark Recognition (OMR) software and a microprocessor built in. It can recognise marks made in specific places on an object. The object usually has a flat surface with a known orientation, e.g. a piece of paper or card which is fed through the reader. But it can be irregularly shaped and randomly orientated, e.g. on a parcel being carried on a conveyor belt .
Most systems use a normal scanner or digital camera to form an image which is then sent to a computer running Optical Mark Recognition (OMR) software
Light / Optical. A light sensor usually uses an electronic component whose electrical properties depend on the light level. Common types are the Light Dependent Resistor (LDR) the photodiode and the phototransistor.
Pressure. A pressure sensor measures the difference between two pressures. One pressure may be zero (a vacuum). Changes in pressure cause mechanical movement in part of the sensor. This movement is then converted into a pressure reading.
Temperature. Temperature sensors may be electronic or optical based.
Electronic temperature sensors include:
Optical temperature sensors include Infra-
Some sensors produce digital signals, 0 s and 1 s. These signals can usually be fed directly to a computer.
Other sensors produce analogue signals, these are variable like the volume control on a television or radio. Analogue signals must be converted to digital ones by an Analogue to Digital Converter before they can be sent to a computer.
A touch pad is an input device often found on
laptop computers and PDAs. They are used a
substitute for a mouse. The user controls a
pointer by moving their finger over the surface
of the touch pad. Tapping on the touch pad
performs the same function as clicking a mouse
Some touch pads also have programmable hotspots
controlled by software. These allow places on the
touch pad to be used for specific functions, rather
like the buttons or wheel on a mouse. e.g. holding
a fingertip on one corner of the touch pad may
launch a particular program, while moving a finger
along the edges of the touch pad may scroll the active window.
Touch screens, are displays which detect the position of a person's finger or some other object. They may have an overlay, similar to that on a concept keyboard. The effect of such overlays allows touch screens to be used to replace the mouse and / or keyboard as the main input device.
Touch screens detect a finger position in several different ways.
Touch screens are often used in mobile phones, iPods and other hand held devices.
The most common method is to have two thin metal sheets which are pushed together when the screen is touched. This is the least sensitive method but also the cheapest to produce and one of the most durable.
Other forms of touch screen use Infra-
More modern touch screens use strain gauges or optical methods.
Control devices are used in control systems. They are able to act on a control signal from a microprocessor and produce some form of mechanical output.
Control devices are also know as actuators.
Some common control devices are:
A computer monitor, also known as a computer screen, computer display or visual display unit (VDU) is a device that can display signals generated by a computer as images on a screen. Most monitors are either cathode ray tube (CRT) or Liquid crystal diode (LCD). Thin film transistor (TFT) monitors are a form of LCD.
CRT, cathode ray tube monitors. The inside of the screen is covered with sets of phosphor dots. These dots are in groups of three and make up a picture element (pixel). Each group contains a red dot, a green dot and a blue dot. The coloured dots are made to glow by being hit with beams of electrons produced by three electron guns at the back of the tube. The electron beams scan across each pixel between 60 and 75 times a second. This is called refreshing.
LCD, liquid crystal display monitors. Each pixel is made up from a layer of liquid crystal molecules suspended between two transparent electrodes which are in turn held between two polarizing filters. An electric charge alters the orientation of the liquid crystal molecules and allows different amounts of light to pass through. The pixels are rectangular and arranged on the screen in rows and columns.
TFT, thin film transistor monitors. One drawback of LCD monitors is that the electrical signals used to control a single pixel can have small effects on other pixels in the same row or column on the screen. TFT is a development of LCD technology which has a transistor built into each pixel to stop these effects.
A plotter is a printing device that is designed for drawing vector graphics.
Plotters produce output by moving a pen across the surface of a piece of paper. This means that plotters are restricted to line art. They can show an area of solid colour by drawing several regular lines, hatching.
Movement of the pen is controlled by a printer control language which sends detailed information like pen up, pen down, draw a line from here to here.
Plotters are mainly used in technical drawing and CAD applications. Here they have the advantage of working on very large paper sizes while maintaining high resolution. Another use has been found by replacing the pen with a cutting head or a laser beam. In this form plotters can be found cutting materials out in the clothing, woodworking and metalworking industries.
A printer is a device that produces hard copy, usually on paper or transparencies. A printer may be attached to a particular computer or it may be fitted with a network interface card (NIC) and attached directly to a network.
The most commonly used printer types are dot matrix, inkjet and toner based (laser / LED).
Dot matrix. These printers use the physical impact of small pins to create precise dots. The pins are held in a rectangular pattern in a small block on the print head. The pins strike an inked ribbon to form a mark on the paper. Dot matrix printers have largely been replaced by inkjet and toner based printers but are still used in cheap, low-
Inkjet. These printers use tiny nozzles that produce very small droplets of ink. They are faster and quieter than dot matrix printers. The printers are often cheap to buy but the ink can be expensive, especially when printing large areas of colour. They also have the disadvantage that pages must be allowed to dry before being handled, otherwise the ink may smudge or run.
Bubblejet printers work in the same way as inkjets but use a different method of spraying the ink.
Toner based, Laser /LED. These work by using a laser or an array of Light Emitting Diodes (LEDs) to create a pattern of static charge on a rotating drum. The drums rotation takes it past a toner reservoir and toner sticks to the drum in the pattern made by the laser / LED. The toner is then transferred to the paper and stuck to it by heat and pressure in a fuser unit. Colour laser / LED printers have four drums, cyan, magenta, yellow and black.(CMYK).
A projector takes a video signal and projects the corresponding image on a projection screen. using a lens system. Projectors are widely used for conference presentations, classroom lessons, and home theatres. There are three common technologies used to produce the image.
Cathode ray tubes (CRT). These normally use three tubes, one for red, one for green and one for blue. They are expensive and bulky and are mainly used in fixed systems. They have the advantage of low maintenance and they do not need frequent bulb replacements like the other types.
Liquid crystal diode (LCD). These contain three LCD arrays, one for red, one for green and one for blue. Light from a halogen bulb is shone through the LCD arrays and lenses focus the three colour beams onto a projection screen. This is the simplest system, making it relatively cheap and one of the most common for home theatres and business use.
Digital light processing (DLP). In these the image is created by microscopic mirrors on a semiconductor chip. Each mirror forms one pixel in the projected image. The mirrors can be moved rapidly to switch the pixels on or off. Colour is produced either by having three semiconductors or by synchronising colour filters with the movement of the mirrors on a single chip.
Speaker and Headphones. These contain an electromechanical device which converts an electrical signal into sound. There are many different designs for making the conversion but most of them are essentially a coil of copper wire around a magnet.
When the electrical signal passes through the wire coil, it generates a magnetic field which causes the coil to move relative to the magnet. The movement is transferred to a thin diaphragm which in turn moves the surrounding air, making the sound.
A hard disk is the commonest form of data storage on home and business computers.
Hard disk storage is also known as backing storage or secondary storage. Hard disks have fast access speeds and a high capacity. The disks are re-
Hard disks have a large storage capacity and at the time of writing, 2013, they are available with up to 4 terabytes (Tb) of space.
The data on a hard disk is stored magnetically, written and read by a head which 'flies' on a cushion of air just a few nanometres above the surface.(1 millimetre = 1,000,000 nanometres)
Most computers have one or more hard drives installed inside the case. They are attached directly to interfaces on the motherboard.
There are also external / removable hard drives available which can be connected to external ports such as USB or Firewire.
Flash media devices contain flash memory. This is re-
Magnetic tape is a re-
Usually, data is written to the tape in blocks with inter-
Tapes are particularly used for backup purposes.
An optical disc is flat disc, usually made of polycarbonate. Data is stored in the form of pits melted into the flat surface by a laser. The data is also read by a laser, the pits reflecting the light differently to the flat surface. The change from a pit to a flat surface gives a binary 1 while two adjacent flats give a binary 0. The binary 1 or 0 is one bit.
The data on optical discs is non-
A compact disc (CD) is flat disc, usually made of polycarbonate. Data is stored in the form of pits melted into the flat surface by a laser. The data is also read by a laser, the pits reflecting the light differently to the flat surface. The change from a pit to a flat surface gives a binary 1 while two adjacent flats give a binary 0. The binary 1 or 0 is one bit.
The data on compact discs is non-
These are pre-
These are purchased as blanks and can then be written to by a CD writer. Once written, the disc cannot be re-
These are purchased as blanks and can be written to by a CD writer. Once written, the data can be erased and the disc re-
There are also mini CDs which hold about 180 Mb of data and business card CDs which hold about 50 Mb.
A digital versatile disc (DVD) is flat disc, usually made of polycarbonate. Data is stored in the form of pits melted into the flat surface by a laser. The data is also read by a laser, the pits reflecting the light differently to the flat surface. The change from a pit to a flat surface gives a binary 1 while two adjacent flats give a binary 0. The binary 1 or 0 is one bit. Most DVDs use dual layer technology to store more data on the disk.
The data on DVDs is non-
These are pre-
These are purchased as blanks and can then be written to by a DVD writer. Once written, the disc cannot be re-
These are purchased as blanks and can be written to by a DVD writer. Once written, the data can be erased and the disc re-
The processor or central processing unit (CPU), is the part of a computer that interprets and carries out software instructions, performs calculations, processes control signals and stores data. The CPU is managed by the operating system.
CPUs are often called microprocessors although a CPU will usually contain other components as well.
A CPU is made up of three parts:
The unit of memory is the Byte. One byte is made up of 8 bits. One bit is a single binary digit and can have a value of 1 or 0.
Computer memory can be Read Only Memory (ROM) or Random Access Memory (RAM).
Computer memory consists of primary and secondary storage.
There are three types of primary storage:
Secondary storage is also known as backing storage, it is slower than primary storage and in most computers the main means of secondary storage is a hard disk.
Details of how ROM and RAM work are not in the IGCSE ICT specification. This is a brief guide, which includes examples of use.
ROM is memory that is written to once and can then be read many times. It does not need refreshing and will retain the data without being powered, for this reason it is called non-
In modern systems, a lot of ROM is replaced by flash memory, since this is also a non-
RAM is memory that can be written to and read from many times. It comes in several forms, the common ones being chip, optical and flash memory. RAM chips require power and must be refreshed many times a second to retain the data stored on them, this is known as volatile memory. It has the advantage of being very fast to access and alter.
Optical RAM is re-
Flash memory is found in items such as pen-
An Operating System is a program or set of programs which control a computer. It manages the hardware and software and provides a way for applications to interact with the hardware.
Some common operating systems are Windows, Linux and Mac OS X.
An operating system will handle the following:
Application software is computer software that enables a user to use a computer to perform a specific task or group of tasks.
Application software includes: