ICT

Topic 1.3 : Peripheral Devices

Topic 1.3 :Peripheral Devices

Peripheral device, also known as peripheral, computer peripheral, input-output device, or input/output device, any of various devices (including sensors) used to enter information and instructions into a computer for storage or processing and to deliver the processed data to a human operator or, in some cases, a machine controlled by the computer. Such devices make up the peripheral equipment of modern digital computer systems.

Types of Peripheral Devices

Peripheral devices are devices that can be connected to a computer, such as a PC or tablet device. Peripherals can be connected inside or outside a computer and can be grouped into three types (see next Figure):

◾ input

◾ output

◾ storage.

▲ Figure 1.34 Data is input from devices such as keyboards and processed by a computer, and the results can then be sent to output devices such as screens

Input

Input peripherals are devices that send data to the computer. They allow the user to control the computer or store data captured from sources outside the system.

KEYBOARDS

Keyboards use buttons known as keys, which users press to input text or to interact with software. Keyboards send data to the computer either using a wired or wireless connection. Different types of keyboards are used for different operating systems, languages and functions, as shown in Figure 1.35.

Combinations of key presses allow the user to access common software commands called shortcuts. Some people learn to touch-type, which is a method of typing without needing to look at the keys. This increases the speed at which these people can input data.

▲ Figure 1.35 Different layouts are provided for different operating systems or language requirements

Figure 1.36 This is an example of a keyboard used with specialist video software; the keys are mapped to specialist commands

POINTING DEVICES

A pointer is used on a screen to select displayed objects. There are several types of device that allow you to control a pointer.

◾ Mouse: A mouse uses an optical sensor to recognize the movement of the device. Its sensitivity can be affected by the surface upon which it is placed. Some mice use roller balls to control the movement of the pointer.

◾ Tracker ball: A tracker ball is rolled to move the pointer. It does not have buttons to press.

Track pad: The track pad surface senses finger movements, touches and presses.

◾Joystick: Joysticks are commonly used on games controllers to move sprites around the game.

◾ Graphics tablet: A graphics tablet is a flat pad that is used with a stylus.

Users use the stylus to draw or write on the graphics tablet. These devices are often used by digital artists and designers.

SCANNER (INCLUDING OCR AND OMR)

A pointer is used on a screen to select displayed objects. There are several types of device that allow you to control a pointer.

Scanners use light sensors to record physical documents as images, which are

then saved as files to the computer.

Software allows scanners to read characters on the document and store the

result in a text file. This is known as Optical Character Recognition (OCR).

Optical Mark Recognition (OMR) software can also be used with scanners

to detect simple marks on a document. A common use for OMR is for

recognising and recording responses to multiple choice tests.

BARCODE SCANNER

A barcode is a pattern of lines and gaps that can be read by barcode scanners, which detect the width of lines and gaps in a barcode. Barcodes are often used on parcels, so that they can be tracked, and on items for sale in shops. The barcode represents letters and numbers which are used to identify the item.

There are two types of barcode:

◾◾ linear

◾◾ matrix.

Matrix codes are also known as QR codes. They are newer than linear barcodes and have some advantages over linear barcodes, such as:

◾◾ they can hold much more information than linear barcodes

◾◾ they can be scanned from any angle.

In South Korea, a supermarket company wanted to open a new shop, but there was no space left on the high street. Instead, the company created a ‘virtual store’ by putting posters of their supermarket shelves in a subway station, as shown in Figure 1.45. Every item pictured on the shelves had its own QR code that shoppers could scan. This allowed people to shop while they were travelling to work in the morning, knowing that their shopping would be delivered to their home that evening.

WEBCAM

Webcams are specialised cameras. They are generally lower quality than camcorders, and may have built-in microphones to capture sound.

They can be used as security cameras and can stream images or video to the internet.

MICROPHONE

A microphone is used to capture sound. It uses a diaphragm which moves when air hits it. This movement produces an analogue electrical signal. A microphone converts the electrical signal to a digital signal with its sound card, which acts as an analogue-to-digital converter.

Small, low-quality microphones are often built into computers and are used for voice recognition, recording speech or allowing VoIP calls using software such as Skype©. Higher quality microphones are often used by recording artists and can be connected to a sound card’s audio input port.

TOUCH SCREEN

Touch screens are used in many devices, including smartphones, tablet devices,

laptops and desktop computers. There are two types of touch screen:

◾◾ resistive

◾◾ capacitive.

When a user presses on a resistive screen, the pressure causes two layers

underneath the screen to touch and make a connection. Resistive touch screens

are more durable than capacitive touch screens, but are harder to read because

more layers reflect more light. In addition, they can only recognise one touch at a

time, so they are not suitable for multi-touch applications.

Under the glass of a capacitive screen, there is a layer of capacitive material.

When a user touches the screen, a small amount of charge flows away from

their finger because humans are conductive. The change in electrical charge

is measured precisely: the closer the finger is to the charged areas, the more

current flows away. This allows the computer to calculate the precise location

at which the screen was touched. Capacitive touch screens are often used in

smartphones.

BIOMETRIC SCANNER

If you have watched a spy film, you may have seen a biometric scanner being used. Biometric scanners work by measuring part of the unique physical characteristics of a user, often multiple times, until a suitable average result is produced. This average result is then stored and future samples are compared against it in order to check whether the person being scanned is the authorised user. This allows the information to be updated so that the saved sample is perfected.

Four examples of biometric scanners are as follows.

◾◾ Fingerprint recognition: These scanners read the patterns of arches, loops and whorls in a human fingerprint. Fingerprints are unique to each individual person, which makes them a useful method of identification, but fingerprints can be obscured, damaged or changed, such as by injury or disease.

◾◾ Facial recognition: These scanners identify the structure of a human face in order to identify an individual.

◾▲ Voice recognition: These scanners require a microphone to capture the voice. They then compare the voice print against a saved original and check to see whether the two prints match. (See page 26 for more information about microphones.)

◾▲ Iris recognition: Like fingerprints, the human iris has a unique pattern, though an iris scan is approximately 120 times more detailed than a fingerprint. This means that iris recognition is 120 times more reliable when identifying people.

CARD READERS

Card readers are used to read data stored on a card that is carried by a user. The data can be used to unlock doors, access secure areas, make payments or track people, parcels and even pet animals.

Cards can carry data using three methods. Each method needs a specialist type of reader.

◾◾ Magnetic strip: This is the least secure method as the data on the magnetic strip can easily be stolen by criminals who put the card through a card reader without the card owner’s knowledge.

◾◾ Programmable chip: Data on a programmable chip is only readable when a correct PIN is entered into the reader. In 2005, the UK introduced the chip and PIN system, which reduced certain types of fraud by 67%.

◾◾ Radio Frequency Identification (RFID) and Near Field Communication (NFC): RFID is a short-range wireless communication method, and Near Field Communication (NFC) is a branch of RFID. RFID tags are cheap and small and they can be included in a variety of objects such as cards, key fobs and smartphones. They contain a unique identification number (ID) that is linked to records in a database. For example, the first image in Figure 1.58 shows a traveler using a prepaid travel card. A unique ID stored on the card links to account information stored in a database. You will learn more about databases in Unit 6 Software skills.

SENSORS

Sensors are used to input data about the physical environment. They can automatically input data without the need for human action. Their output is then processed by a computer. Sensors are one of the main features of smart devices such as smartphones and smart environments such as smart homes.

The use of sensors has many benefits, such as:

◾◾ they can be placed in remote or dangerous places

◾◾ they can monitor continually

◾◾ they remove the possibility of human error

◾◾ they can sense things that people cannot (such as small changes in pressure or gas levels)

◾◾ the data is easily (sometimes automatically) converted to a digital form.

There are many different types of sensor to allow for the monitoring of a range of environmental factors. Some of these factors are:

◾◾ light

◾◾ moisture and humidity

◾◾ temperature

◾◾ proximity and distance

◾◾ motion and movement (such as Passive Infrared (PIR) sensors)

◾◾ pressure.

OUTPUT

Output peripherals are connected to a computer and output the results of the computer’s processing in various forms, including:

◾ electronic display

◾ printed text

◾ video

◾ audio

◾ tactile (touch) forms.

MONITOR

Monitors allow users to see the output from the computer on an electronic display. Features of monitors include:

◾◾ screen size, which is measured diagonally

◾◾ resolution, which is measured in pixels (see pages 9–10 for information about pixels and screen resolutions)

◾◾ energy efficiency measures, such as going into a low-power standby mode if no input is detected.

Some monitors also use touch screen technology (see page pages 26–27 for more information about touch screens).

PRINTER

There are three types of standard printer: dot matrix, inkjet and laser.

Dot matrix: These printers are sometimes called ‘impact’ printers. This

is because the print is made by hitting or ‘impacting’ the paper through a

ribbon of ink, and this process is very noisy. The paper often has a number

of carbon copy layers so it can make several copies of the same document

as it prints it.

◾◾ Inkjet printers: These printers use cartridges containing different coloured ink. Black ink is held in a one cartridge, while the colour cartridge is often split into three colours: cyan, magenta and yellow. Tiny dots of these inks are sprayed onto the paper to form images or text.

◾◾ Laser printers: These printers contain a rotating cylinder or drum that holds an electrical charge. A laser is used to discharge certain points on the drum and ‘draw’ an image. Electrically charged toner is attracted to those points on the drum and is heated onto paper that is passed over the drum.

PLOTTER

Plotters are used by a variety of professionals, including product designers, architects, engineers and cartographers. The plotter draws high-quality images created in Computer Aided Design (CAD) software onto large sheets of paper.

It does this by moving a pen across the paper to draw the lines, and the pen can be raised away from and lowered onto the sheet of paper. Some plotters can also roll the paper backwards and forwards.

3D PRINTER

Three-dimensional (3D) printers create real-life versions of digital models. These printers work by adding layers of heated material from the bottom of the model all the way to the top. 3D-printed models take a long time to create.

3D printers are often used to create complex items, sometimes with working parts. Some of these items could not be assembled in any other way. Examples of 3D-printed items include aero plane parts, artificial limbs, prototype models of cars and even food such as pasta and chocolate.

DATA PROJECTOR

Data projectors are used for home entertainment, such as watching television or playing games, and for giving presentations in classrooms and business meetings. They project image into a screen or wall.

They have the following features.

◾ Light bulbs: These bulbs can have various brightness levels (measured in lumens) and are expensive to replace.

◾ Resolution: Like monitors, they use different quality screens (see page 9–10 for more about screen resolutions).

◾ Zoom functionality: The projected image can be made larger by enlarging the image using either optical zoom or digital zoom.

◾ Portability: Some smaller and lighter projectors are available, and these are easier to move around.

SPEAKER

Speakers allow a computer to output sound. Speakers often come in pairs to provide stereo sound.

Multiple speakers are commonly used to provide surround sound in home entertainment systems. These speakers need a special amplifier that can deliver different levels of sound to each speaker to provide spatial awareness.

A single speaker is usually used to provide low-quality audio feedback to a user. These speakers are often small and low-quality, and are often found in alert systems such as alarms and buzzers.

CONTROL DEVICE

Control devices are also known as actuators, and they are components of a system that make something happen in the real physical world. These devices are often mechanical. Examples of actuators include:

◾◾ valves

◾◾ pistons

◾◾ heaters

◾◾ coolers

◾◾ motors.

Storage DEVICES

Storage devices are used to store data or software that is used in a computer

system.

Storage devices can be either internal or external. Internal drives connect directly to the computer’s motherboard. External devices are connected to the computer’s motherboard through the different ports and adapters on the computer’s exterior.

There are different types of storage device:

◾◾ Hard disk drives (HDD) contain hard disk media. The drives provide a connection from the disk to the motherboard, either directly or using a wireless adapter like Wi-Fi or a wired port like USB.

◾◾ Solid state drives (SSD, often referred to as flash drives) contain flash memory media. They are otherwise identical to hard disk drives.

◾◾ Optical disk drives contain optical disk media. Newer drives are often compatible with older media. For example, a disk drive that can read Blu-ray media can also read DVD and CD media. This is known as backwards compatibility.

SECONDARY STORAGE (STORAGE)

Secondary storage is often referred to as ‘storage’. However, it should not be confused with primary storage or main memory, which are terms sometimes used to refer to Random Access Memory (RAM) or Read Only Memory (ROM).

You will learn more about RAM and ROM on pages 59–61. Secondary storage is non-volatile, which means it will not lose data when the system’s power is turned off.

Secondary storage is used for:

◾◾ storing a document for future use

◾◾ storing an application, ready to be loaded into RAM when the user opens the application.

◾◾ virtual memory (see page 60).

MEDIA

Hard disks

Hard disks are made up of many concentric platters. These platters make up a cylinder that spins on a central spindle. A read/write head moves on an arm across tracks on the platter. The amount of time that it takes the read/ write head to access data on the tracks is determined by how fast the cylinder of platters spins and how fast the read/write head is moved across the tracks.

When reading, a read/write head changes the magnetic field into electrical current. When writing, it transforms electrical current into a magnetic field.

Typical spin speeds are 5400 revolutions per minute (rpm) or 7200 rpm. The average seek time for a read/write head is 4–15 milliseconds (ms).

Optical media

Types of optical media include CDs, DVDs and Blu-ray disks.

◾◾ CDs can store up to 700 MB of data. The data is written to the disk using a

laser, which writes data to a plastic layer beneath layers of aluminium and

acrylic.

◾◾ DVDs look very much like CDs. Data is written to DVDs using a shorter

wavelength of red laser light, which allows DVDs to store more data. They

can store 4.7 GB on a single-sided, single-layer disk. Double-sided, duallayer

disks can store as much as 18 GB.

◾◾ Blu-ray disks are similar to CDs and DVDs, but use a scratch-protection

coating. Violet laser light is used to store data at greater density than the red

laser light used in DVDs. They can store 25 GB on a single-sided disk, and

double-sided disks can store 50 GB.

All optical media is recordable and is known as CD-R, DVD-R or BD-R. Some

CDs and DVDs can be rewritten (CD-RW, DVD-RW), and some Blu-ray media

can be written then erased and rewritten (BD-RE).

Flash media

Flash media are more energy-efficient than hard disks as they do not have moving parts. For the same reason, they are also less likely to fail when they are moved around. This makes them suitable for use in portable devices.

Magnetic tape

Magnetic tape was originally designed to record sound, but it is now also used to store data.

Storage media store data in binary form. This means that each bit of data holds one of two values: 0 or 1. Different media types interpret 0 or 1 differently.

◾◾ Hard disks change the magnetic charge of a platter to either negative or positive, depending on whether the value is 0 or 1.

◾◾ Optical media use tiny bumps on the disk’s surface to represent 0 and 1.

◾◾ Flash media use different levels of electrical charge, held in tiny individual cells, to represent 0 or 1.

◾◾ Magnetic tape changes the magnetic charge of the tape to either negative or positive, depending on whether the value is 0 or 1.

What is difference between MiB and MB?

A mebibyte is equal to 2²⁰ or 1,048,576 bytes. A megabyte is equal to 10⁶ 1,000,000 bytes.

One mebibyte equals 1.048576 megabytes.

The relatively small difference between the two is, in part, why they are often used synonymously.

Page updated

Report abuse