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Input and output devices

Chapter 2 – Input and Output devices

Keyboards: It is an input device that allows the user to input text, numbers, and instructions into the computer. Most use the qwerty layout. The ergonomic layout was developed to prevent certain health issues or to make it easier for people with limited arm/wrist movements to use. Some uses are:

• Input data in application software

• Input commands into the computer

Advantages:

• Fast entry of text 

• Easy to use

• Easier to do verification checks while entering data

Disadvantages:

• Difficult to use by people with limited arm/wrist movements

• Slow method when compared with direct data entry

• Takes up desk space

Concept keyboards: These keyboards make use of icons or phrases instead of letters removing the need to type commands or text. They are mainly used in for example vending machines or self-ordering stations in restaurants. Some features include:

• They are waterproof

• Allows for fast data entry

• They are tamper resistant in certain applications

Numeric keypads: A numeric keypad is used to enter numbers only. Some uses are:

• Automatic Teller Machines (ATM’s)

• Mobile phones

• Point of sale terminals (POS)

• Chip and Pin devices 

• Fast entry of numerical data into a spreadsheet

Advantages:

• Faster than keyboards in entering numerical data

• Small and portable

Disadvantages:

• Sometimes order of the numbers isn’t intuitive

• Has small keys making input more difficult

• If one key doesn’t work the entire system would be ineffective

Mouse: It is a pointing device that the user can use to control the pointer on the screen. There are also two buttons where the left one is used to select and the right to open a drop-down menu. Some uses are:

• Opening, closing, and minimising software

• Drag and Drop

• Image editing

• Control of pointer on screen

Advantages:

• Faster way to choose options

• Takes up less desk space

• Lightweight

• Easy to surf through the internet and applications

Disadvantages:

• Hard to use by people with limited arm/wrist movements

• Hard to use on non-flat surfaces

• Easy to damage, lose, or get stolen

• Can’t enter text data

Tracker balls: Similar to a mouse but a ball on the top or side of the mouse that can rotate controls the pointer on the screen. Some have a third mouse button that serves as a double click. This mouse is easier to use by people with limited arm/wrist movements.

Advantages:

• Easier to use by people with disabilities

• Doesn’t need same fine control as a mouse

• More robust

• Less desk space than a mouse

• More accurate positioning of mouse

• Can be used on non-flat surfaces

Disadvantages:

• Expensive

• User needs training as it isn’t standard equipment

• Easy to damage, lose, or get stolen

Touch pads: Same as a mouse except dragging your finger across a touch pad controls the pointer on the screen. Two buttons bellow the touchpad simulate left and right mouse buttons.

Advantages:

• Can be used on non-flat surfaces

• Part of the computer making it portable

• Faster way to choose options

• Easy to surf through the internet and applications

Disadvantages:

• Hard to use by people with limited arm/wrist movements

• Harder to control pointer as accurate as a mouse

• Hard to use drag drop functions

Remote control: It is a device that is used to control operations of another device remotely with use of infrared signals. The buttons on the keypad are used to make selections.

Advantages:

• Can be operated from reasonable distances

• Can be used in operations too dangerous for humans

• Easy to use in control applications

Disadvantages:

• Difficult to be use by people with limited arm/wrist movements

• Easy to block signal. For example, a wall

• Easy to damage/ lose

Joysticks: It is a device that makes use of stick whose movements are sent into the computer to control a pointer. There are other buttons to make selections and even one on top for simulating for example firing a weapon.

Advantages:

• Easier to navigate screen than keyboards

• More realistic control in for example simulations

• Can be used easily

Disadvantages:

• Not easy to control on screen pointer 

• Hard to use by people with limited arm/wrist movements

• Difficult to enter text

Touch screens: User can make selections by touching a button or icon on the screen.

Advantages:

• Fast entry of options

• User friendly

• No need for external pointing device

Disadvantages:

• Limited options

• Screen can get dirty tampering with responsiveness of screen

• Can lead to health problems with constant use. (Example RSI)

Driving wheel: It is a device that allows the user to simulate the wheel of a car. The movements of the wheel are picked up by sensors, as well as buttons and pedals to simulate a realistic feeling of driving.

Advantages:

• Easier than keyboard or joystick to control steering movements

• It is more realistic 

• Can be used by people easily

Disadvantages:

• It is expensive

• Movements can be too sensitive

• Unless simulation is of high-quality feedback to wheel could be non-existent

Scanners: Scanners are used to enter hardcopy information into the computer. The hardcopy is placed in a scanner and is then scanned by a light source to produce a computer readable image.

Uses:

• Scan in old/valuable/books

• Scan in photographs

• Scan in documents in specific formats 

• Scan in barcodes at POS terminals

Advantages:

• Much faster and accurate than typing in the document again

• Images can be stored and edited later

• Possible to recover damaged documents

Disadvantages:

• They are slow at scanning

• Quality can be limited to the resolution of scanner

• Take up a lot of space

• Noisy

Digital cameras: Digital cameras are devices that store images on a memory card after taking a photo

How to download photos from a digital camera:

1. Use a USB connection or insert a memory card

2. Download photograph from cloud, Wi-Fi, Bluetooth, or the inserted memory card in a memory card reader connected to the computer

3. Images are then uploaded and used by the user 

Advantages: 

• Easy to produce high quality images

• Easier to produce high quality images 

• Easier and faster to upload

• A memory card can store several hundred photos

Disadvantages:  

• Need to be computer literate to operate camera and modify images taken

• Artistry is lost as software can correct errors in images

• The resolution isn’t as good as traditional cameras

• Images often need to be compressed to reduce memory used

Video Camera’s: It is a device that takes a series of still images and stitch them together to form a video.

Advantages:

• It is easy to manipulate video footage using specialised software

• DV format gives a very high-quality image which lends itself to effective editing 

Disadvantages:

• To take video footage it takes up more memory than still images

• It can be costly as there isn’t enough memory in a memory card to store several videos

Microphones: It is a device that makes use of acoustic sensors to input sound. This is transfer through an Analogue to Digital Converter (ADC) to the computer as a digital signal. The sound card also does this automatically and also acts as an ADC.

Advantages:

• Faster to read text than type it in 

• Can be used in voice activation systems

• Can manipulate sound in real time 

Disadvantages:

• Takes up a lot of memory

• Voice recognition isn’t as accurate as typing it in

Sensors: They are devices that input data consisting of physical quantities. This data is in analogue format but a computer only understands digital format. Therefor requiring an ADC.

Types of sensors:

• Temperature sensor – Used to input temperature readings
• Moisture sensor – Used to enter reading on amount of moisture in air

• Oxygen/Carbon Dioxide sensor – Used to input readings of quantity of oxygen and carbon dioxide

• Light sensor – Measuring light levels in the environment

• Infra-red sensor – Picks up any movement within a range of the infra – red light

• Pressure sensor – Detects amount of pressure upon a surface

• Acoustic sensor – Picks up sound readings

• Motion sensor – Detects motion in a set area

• PH sensor – Used to input PH level of a substance

• Proximity/distance sensor – Serves same function as motion and infrared – sensors

Advantages:

• Accurate readings

• Continuous readings
• Actions and warnings in response to readings immediately taken

• Automatic system

Disadvantages:

• A faulty sensor could provide false readings

• Can’t react to unplanned circumstances

Graphics Tablet: It is a device used with a stylus pen to produce freehand drawings on a screen.

Advantages:

• It is possible to modify drawings before they are inputted

• Very accurate method of drawing

• Can record levels of pressure

Disadvantages:

• Expensive

• Longer time to produce drawings than with pen and paper

• Menus aren’t easy to use

• Large drawings are expensive to use

• Easily damaged

Web cams: Similar to digital and video cameras but are connected with the computer. It doesn’t have memory instead it inputs data directly to the computer.

Advantages: 

• Can be on constantly

• Allow for face-to-face conferencing online

Disadvantages: 

• Limited features

• Need to be connected to the computer

Light pens: It makes use of sensors that pick-up change in light and sends signals to computer. They only work with CRT monitors as they use an electron beam to produce a display.

Advantages:

• Very accurate 

• Small and portable

• Easy to use

Disadvantages:

• Problems with lag

• Only work with CRT monitors

• Dated technology

Magnetic Stripe readers: They are used to read magnetic stripe that contains private information.

Advantages:

• Fast data entry

• Error free

• Secure

• Robust

• Not affected by damaging substances (For example water)

Disadvantages:

• If magnetic stripe is damaged data is lost

• Doesn’t work at distance

• Data can’t be read by humans

• Can be damaged by strong magnetic fields

Contactless card readers: All customers with a contactless card may pay for items up to 25 $ without a PIN. All contactless cards contain a chip that emits radio waves. The reader can pick up these signals when the card is within a few centimetres

What are the steps of using one?

1. Customer looks out for contactless symbol on reader at the POS terminal

2. Shop assistant enters required amount

3. The terminal informs customer to present card

4. Customer holds card near contactless symbol on the reader

5. The terminal display will show if transaction is completed 

Advantages:

• Fast transactions

• Customers doesn’t have to worry about typing errors

• Retailer doesn’t have access to personal data

• Hard to damage

Disadvantages:

• Expensive 

• Has a maximum withdrawal amount 

• Transactions could be taken without card holders’ knowledge

• A thief with a reader can monitors transactions

• Can easily be lost or stolen

Chip and Pin readers: The reader requires the card holder to insert their card into a slot where the chip on the card can be read. The user then must enter a pin for the transaction to take place

Advantages:

• Secure 

• Robust

Disadvantages:

• Fraud if a person sees your pin while you are entering it

Radio Frequency I dentification Readers (RFID): An RFID tag emits radio waves that can be picked up by a reader with an antenna. The RFID tag is made up of two things:

• A microchip that stores and processes data

• An antenna that sends and receives data

Advantages:

• Robust

• Fast read rates

• Can be read from a distance

• Allows read and write operations

• Bulk detection possible

Disadvantages:

• Tag collision

• Easy to jam/interrupt

• Easy to hack

• Expensive

Magnetic Ink Character Recognition (MICR): It can only read characters in magnetic ink in a standard font. Used in reading of bank cheques 

Advantages:

• Very secure

• Very accurate

• Can be read even when written over

Disadvantages:

• Only certain characters can be read

• Expensive

Optical Mark Recognition (OMR): It makes use of light that shines off sheet and detects reflectivity of the light. Places marked with pencil or pen can be read but can only be used in forms with limited options.

Advantages:

• Very fast 

• Very accurate

Disadvantages: 

• There can be problems if forms have been filled incorrectly 

• Forms must be designed carefully so that position of options are accurate

• Optical Character Recognition (OCR): Can convert scanned text into computer readable formats.

Advantages:

• Very fast

• Can read handwriting

• Allows for wider range of answers 

Disadvantages: 

• Not very accurate

• Cant read bad handwriting correctly

OMR vs OCR
Involves shading options so answers are limited to choices provided	Involves writing answer soanswers are more diverse
Detects marks made and compares to a template form	Can read hand writing but bad handwriting causes errors
OMR read position of mark making it ideal for MCQ	Mostly used for conversion of hard copy documents to a digital format
Simple recognition of forms but are expensive	Requires complex recognition system
Faster to complete OMR than OCR forms	Slower to complete OCR forms
More accurate than OCR	Isn’t as accurate as typed in documents

Barcode readers: These handheld scanners can read data in the form of a barcode.

Advantages:

• Fast data entry 

• Automatic stock control

Disadvantages:

• Expensive to administrate

• Easily damaged or swapped

Quick Response Codes (QR codes): There are made up of a matrix of dark squares on a light background and are a form of barcode that send a person to a website upon scanning it.

Advantages:

• Stores website addresses

• No need for user to key in address

• Can be damaged but will still exist and to a certain degree still be scanned with damages

Cathode Ray Tube Monitors (CRT monitors): It makes use of an electron gun shooting against a phosphor screen. The picture is made up of dots that are coloured red, green, blue the intensity of each colour can form various colours.

Advantages:

• Work with light pens

• Better viewing angle than TFT monitors

Disadvantages:

• Heavy

• They run very hot and can catch fire

• They flicker

• Use up a lot of power

Thin Film Transistor Monitors (TFT monitors): Screen is made up of thousands of pixels which are made up of transistors controlled by a microprocessor. Each pixel is made of 3 transistors of red, green, blue the intensity of each forms various colours for the pixel. The monitor makes use of LCD backlighting. 

Advantages:

• Light weight

• Produce glare

• Consume less power

Disadvantages:

• Angle of viewing isn’t as good as CRT

• Definition not as good as CRT

LCD and LED monitors: Liquid Crystal Display (LCD) makes use of liquid crystal diodes grouped together as pixels. Each pixel consists of 3 diodes red, green, blue although some systems use a fourth yellow diode to make more vivid images. It also makes use of Light Emitting Diodes (LED) as backlighting. 

OLED monitors: Organic Light Emitting Diodes makes use of organic films sandwiched two charged electrodes one metallic cathode and one glass anode and when an electric field is applied to them, they produce light. Making it as self-contained system without backlighting. The pixels consist of red, green, blue, and green diodes.

Multimedia Projectors: They receive signals in analogue format and digital formats. The projector receives the images projecting it magnified on a flat surface.

Advantages: 

• Avoid need of several connected computers

• Enables multiple people to see a single presentation 

Disadvantages:

• Expensive

• Difficult to set up 

• Images projected are fuzzy

Laser Printers: Laser printers produce high quality images. Makes use of buffer memories before printing.

Advantages:

• Prints fast

• They can handle large print jobs

• The quality is consistently high

• Toner cartridges last a long time

Disadvantages:

• Only really fast if several copies are made 

• Colour laser printers are expensive to maintain 

• Produces harmful ozone gas

Inkjet Printers: Produces good quality hard copy without use of large buffers, so it prints one document at a time and sometimes pauses for more data to be received.

Advantages:

• High quality output

• Cheaper 

• Lightweight

• Don’t produce ozone

Disadvantages:

• Slow output

• Can’t do large print jobs

• Printing can smudge if handled incorrectly 

• Can be expensive if used often as cartridge run out faster than laser printers

Dot Matrix Printers: It is a type of impact printer where a print head is pressed against an ink ribbon.

Advantages: 

• Can be used in unkept environments

• Very cheap to run

• Easy to use in continuous stationary

• Carbon and multi part outputs can be produced

Disadvantages: 

• Very noisy

• Initially costly

• Very slow

• Poor quality output

3D – Printers: They allow the user to print three dimensional solid, and working objects. A 3D – printer prints the object layer by layer with a special resin, powdered metal, paper, or ceramic. Virtually a 3D – printer can print any geometrical shapes as well as functioning prototypes.

Some facts about 3D printers are:

• 3D printers use addictive manufacturing (Building an object layer by layer) in contrast to traditional subtractive manufacturing (The removal of material to form an object).

• Direct 3D – Printing using inkjet technology involving a print head that moves left to right and up and down allowing build up of an object layer by layer

• Binder 3D – Printing is similar to direct 3D – Printing but first sprays dry powder and then a binder (Type of glue) to form a solid layer. Allowing printing of layer in two passes. 

Steps to create a solid object:

1. A design is made using computer aided design (CAD) software

2. The final design is then imported to specialized software to convert it into a format understood by the 3D – Printer 

3. The 3D – Printer is set up for the solid object to be printed

4. The object is built up layer by layer. The time this takes is dependent on the thickness of layers, materials, and the size of the object

5. The object is removed from the 3D – Printer and is now Prepared (For example removal of excess material)

Advantages: 

• Manufacturing of items have become easier

• Short amount of time for designs to be converted into working prototypes

• Parts of machinery no longer made can be manufactured with 3D – Printers

• Medical benefits

Disadvantages:

• Job losses

• Can be used to produce illegal material

• Can be use to print copy right items

Plotter: Plotters make use of coloured pens moved around by a computer

Advantages:

• They can print on large sheets 

• Print quality is extremely high

• Plotters can do cut out designs 

Disadvantages:

• Very slow

• Very expensive

Speakers: Digital data is converted into analogue data using an analogue to digital converter (DAC). The speakers amplify this analogue signal.

Advantages: 

Everyone in the room can hear the sound 

Can help blind people use a computer as text can be turned into sound 

Disadvantages:

Output from speakers can disturb people 

High quality speakers can be expensive

Actuators: Actuators and transducers and are used to take analogue signal and convert them into some kind of motion. Digital signals are sent from the computer to a DAC and the analogue signals are then sent to the actuators to take an action.

There are 4 main devices that actuators can control they are:

• Motors

• Buzzers

• Lights 

• Heaters

Transducers: Transducers are devices that changed variation in a physical quantity into an electrical signal. An example of these systems would be like this:

Sensors -> ADC -> Microprocessor -> DAC -> Buzzer, Motors, Lights, Heater