chapter 2

• Input devices allow data to be input into a computer
• Output devices allow data to be output from a computer
• Examples of input devices and their uses:

  • Keyboard: inputting data into applications, typing commands into a CLI Interface
  • Numeric Keypad: inputting numeric data into ATMs, POS Terminals, Chip and Pin, Mobile Phones, etc.
  • Mouse: controlling the pointer on the screen to select windows, clicking icons, menu options, and positioning the pointer
  • Touch Pad: used as a pointing device on a laptop
  • Tracker Ball: used by users with limited motility in their wrist (RSI)
• Advantages and disadvantages of input devices:

  • Keyboard: easy and familiar to use, fast entry of text into a document, slower method compared to direct data entry
  • Numeric Keypad: straightforward to enter numeric data like pins or prices at a POS, keys can be too small, difficult to type letters
  • Mouse: easy to navigate through menu options, quicker to select an option compared to using a keyboard, easily damaged, flat surface required
  • Touch Pad: part of the keyboard so no need for a separate device, more difficult to use compared to a normal mouse
  • Tracker Ball: easier to use compared to a mouse, more accurate positioning of the pointer, tend to be more expensive, not familiar to users
• Examples of output devices and their uses:

  • Remote Control: used to control TV channels and menu options, multimedia systems, industrial applications
  • Joystick: used in computer games and simulators
  • Driving Wheel: used by gamers in computer games (racing/driving), used in simulators
  • Touch Screen: used on mobiles/tablets, point of sale (POS), interactive whiteboards
  • Scanners: used to scan documents or photographs
  • Digital Cameras: used to take photographs and small video clips
• Advantages and disadvantages of output devices:

  • Remote Control: can be used from a distance, the signal could be blocked by obstacles or walls
  • Joystick: easier to use compared to a keyboard, more difficult to use compared to a normal mouse
  • Driving Wheel: driving experience is more accurate than using keyboards, more expensive, movement could be too sensitive
  • Touch Screen: very easy to use and select options, options could be selected accidentally, screen can get dirty
  • Scanners: copies can be created, quality is dependent on resolution settings
  • Digital Cameras: higher resolution images can be stored on memory cards, no need to develop a film, transferring, storing, and editing images can be complicated
• Role of Measurement Applications:

  • Sensors are placed to measure physical variables
  • Data from sensors are measured in analogue and then converted to digital signals using a converter
  • Examples of sensors and their applications:
  • Temperature: control a central heating system
  • Moisture: monitor moisture levels in soil in a greenhouse
  • Light: switch on/off street lighting, car headlights when dark
  • Infra-red: detect intruders in a burglar alarm system, count people entering or leaving a building
  • Pressure: detect intruders in a burglar alarm system, check the weight of an object
  • Gas (O2 or CO2): pollution monitoring in rivers or the air, check for CO2 leaks in a power station
  • PH: monitor acidity/alkalinity levels in soil in a greenhouse, pollution monitoring in rivers
• Role of Microprocessor in Control Applications:

  • Sensor readings are compared to pre-set values inputted by the user
  • If sensor readings are below or higher than the pre-set value, a signal is sent to the actuator to change physical conditions
  • Process is constantly repeated
  • Examples of control applications:
  • Greenhouse: compares light, temperature, moisture to pre-set values, controls light on/off, heater on/off, motor open/close windows
  • Patients Vital Signs: compares vital signs (heartbeat, blood pressure, temperature) to pre-set values, buzzer alerts staff to any vital signs below expected values
• In multicellular organisms, the distance for substances to enter cells is larger due to a higher surface area to volume ratio
• Multicellular organisms require specialised exchange surfaces for efficient gas exchange of carbon dioxide and oxygen
• The process of comparing vital signs to pre-set values involves:

  1. Input devices called sensors taking readings

  2. The microprocessor comparing the readings to the preset values

  3. The computer sending a signal to output devices called actuators to change physical conditions
• Examples of input devices and their uses include:

  • Magnetic Strip Readers: used for bank cards, arcade cards, security/hotel room access, and gift cards
  • Chip and Pin Readers: used for secure payments at POS terminals
  • Contactless Cards Readers: used for quick payments without entering a PIN number
  • Radio Frequency Identification (RFID): reads information stored on tags using radio waves
• Advantages of Magnetic Strip Readers:

  • Fast data entry compared to keyboard
  • Secure and error-free
  • Not affected by water and robust if dropped
  • Easily updated

  Disadvantages:

  • Stripe could become unreadable if scratched
  • Does not work at a distance
  • Easily lost or misplaced
• Advantages of Chip and Pin Readers:

  • Secure method of payment
  • Less likely for the chip to be damaged compared to magnetic swipe

  Disadvantages:

  • The pin could be read by someone watching
  • Fraudulent machines can copy card details
• Advantages of Contactless Cards Readers:

  • Quicker transactions
  • No need to use a PIN
  • Encrypted transaction data

  Disadvantages:

  • Less secure than chip and pin
  • Anyone could use the card if lost
  • Easier for thieves to copy card details
• Advantages of Radio Frequency Identification (RFID):

  • Can read objects from a distance
  • Can read in bulk
  • Very fast reading with quick response
  • Allows read/write operations
  • Can read biometric readings

  Disadvantages:

  • Radio signals can be jammed or hacked
  • More expensive than a barcode
  • Tags could interfere with each other
• Optical Mark Reader (OMR) is used to read marks written in pen or pencil for multiple choice exams, surveys, and lottery tickets. Advantages include fast data input and accuracy
• Optical Character Reader (OCR) scans text from hardcopies and converts it into an editable form. Advantages include faster data entry and less chance of errors
• Barcode Scanners are used to scan barcodes containing product information. Advantages include quick and accurate data entry
• Quick Response (QR) codes are scanned using a mobile phone camera to direct customers to websites or provide information. Advantages include storing a good amount of information and working even if slightly damaged
• Output devices and their uses:

  • CRT Monitor
• Output devices that are commonly used in computing include:

  • CRT monitors
  • Flatscreen monitors
  • Touch screens
  • Projectors
  • Inkjet printers
  • Laser printers
  • Dot Matrix printers
  • Plotters
  • 3D printers
  • Speakers
• CRT monitors:

  • Use: Primary output display for computers
  • Advantages:
  • Cheaper than other monitors
  • Can be used with light pens
  • Disadvantages:
  • Consumes more power
  • More likely to overheat
  • Takes up more desk space
  • Not ideal for eyes after long use
• Flatscreen monitors:

  • Use: Have taken over from CRT as primary output display for computers
  • Advantages:
  • Smaller and lighter, requiring less desk space
  • Consumes less power and generates less heat than CRT monitors
  • Disadvantages:
  • Can be more expensive compared to a CRT monitor
• Touch screens:

  • Use: A computer display screen that is also an input device
  • Advantages:
  • No need for additional input devices or buttons
  • Menus and interface are generally easy to use
  • Zoom in and rotation is possible
  • Disadvantages:
  • Screen could become damaged, dirty, less visible
  • Difficult to input high volumes of information compared to using a keyboard
• Projectors:

  • Advantages:
  • Able to project onto a big screen allowing more people to see the output
  • Users can gather around one screen, main focal point in classrooms
  • Disadvantages:
  • Output resolution may not be the same quality as other devices
  • Obstacles could affect or block the projection
  • Expensive to buy and difficult to set up
• Inkjet printers:

  • Use: When low output volumes are required, such as for home use
  • Advantages:
  • Cheap high-quality printing
  • Small in size, taking up less desk space
  • Disadvantages:
  • Ink cartridge can run out quickly and be expensive to replace
  • Slow printing compared to laser printers
• Laser printers:

  • Use: When high output volumes are required, such as in schools or offices
  • Advantages:
  • High-quality printing
  • Fast printing, especially in high volumes
  • Disadvantages:
  • More expensive to buy compared to inkjet printers
  • Colour laser printers are more expensive to run compared to black and white laser printers
• Dot Matrix printers:

  • Use: For shop receipts, airline tickets, and when duplicates are required
  • Advantages:
  • Not affected by hot/dusty environments
  • Can print carbon copies
  • Disadvantages:
  • Very slow printing
  • Poor quality printing
  • Noisy compared to other printers
• Plotters:

  • Use: When large format printing is required, such as for banners, billboards, signs, and posters
  • Advantages:
  • High resolution printing compared to laser and inkjet printers
  • Large printouts
  • Disadvantages:
  • Generally expensive to buy and maintain
• 3D printers:

  • Use: To produce solid objects by building layer upon layer, for applications like prosthetic limbs, manufacturing parts, medical applications, and construction
  • Advantages:
  • Products can be customized
  • Prototypes can be created quickly
  • Disadvantages:
  • Very expensive printer
  • Counterfeit products could be created
  • Dangerous objects could be printed if used inappropriately
• Speakers:

  • Use: To output sound, essential for video conferencing, movies, computer games, etc.
  • Advantages:
  • Speakers can be used wirelessly using Bluetooth technology
  • Sounds can be amplified
  • Disadvantages:
  • Not as personal compared to headphones, can be heard by everyone
  • An underpowered amplifier playing at high volumes can damage a speaker
• Other output devices include:

  • Motors (used in washing machines, control fans, and robot arms in manufacturing)
  • Buzzer (used in burglar alarms, microwave ovens, and sporting events)
  • Heater (used to increase temperature in central heating systems, greenhouses, and ovens)
  • Lights (used in security lights, car dashboards, and greenhouses)