Cambridge IGCSE0417

Input devices and their uses

Information Communication Technology 0417 Chapter Notes

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Input devices and their usesDirect data entry and associated devicesOutput devices and their uses
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In this chapter

  1. 1Introduction to Input Devices
  2. 2Manual Input: Keyboards & Pointing Devices
  3. 3Manual Input: Touch Screens
  4. 4Direct Data Entry: Scanners & Readers
  5. 5Direct Data Entry: Card & Biometric Readers
  6. 6Input Devices: Sound & Image Capture
  7. 7Sensors as Input Devices

1. Introduction to Input Devices

An input device is any piece of computer hardware that sends data and control signals to a computer's central processing unit (CPU). The computer then processes this data to perform a task or produce an output. Without input devices, you would have no way to interact with a computer. Input devices are broadly classified into two categories: Manual Input Devices, which require a human to physically enter data (like typing on a keyboard), and Direct Data Entry (DDE) devices, which capture data automatically from a source (like a barcode scanner reading a product code).

Key term

Input Device: A peripheral piece of hardware used to provide data and control signals to a computer's information processing system.

Examiner insight

Examiners expect you to not only name input devices but also correctly categorise them as either manual or direct data entry.

Fun fact

The first computer mouse was invented in 1964 by Douglas Engelbart. It was made of wood, had one button, and two wheels underneath to track movement.

Worked example 13 marks

For each of the following, state whether it is a Manual Input Device or a Direct Data Entry (DDE) device:(a) Keyboard,(b) QR Code Scanner,(c) Mouse.

  1. 1

    Step 1: Define Manual Input. This requires a person to actively enter data, often character by character or through direct manipulation.

  2. 2

    Step 2: Define Direct Data Entry (DDE). This involves capturing data automatically from a source with minimal human intervention.

  3. 3

    Step 3: Apply the definitions.(a) A keyboard requires a person to type, so it is a Manual Input Device.

  4. 4

    Step 4: Apply the definitions.(b) A QR code scanner reads data from a code automatically when pointed at it, so it is a Direct Data Entry device.

  5. 5

    Step 5: Apply the definitions.(c) A mouse requires a person to move it and click, so it is a Manual Input Device.

Recap

  • Input devices are used to get data into a computer for processing.
  • There are two main types: Manual Input and Direct Data Entry (DDE).
  • Manual input requires a human operator to enter the data.
  • DDE devices capture data automatically, reducing human error.

Quick check

  1. What is the fundamental difference between a manual input device and a DDE device?2 marks

2. Manual Input: Keyboards & Pointing Devices

Keyboards and pointing devices are the most common manual input devices. A standard QWERTY keyboard allows users to type text, numbers, and symbols. Numeric keypads are smaller keyboards, often used for rapid input of numbers in financial applications. Pointing devices control the cursor or pointer on a graphical user interface (GUI). The most common is the mouse, which detects 2D motion relative to a surface. Other pointing devices include touchpads (or trackpads), commonly found on laptops, which allow users to control the cursor with their finger.

Key term

Pointing Device: An input device that allows a user to control a pointer or cursor on a screen to select objects in a graphical user interface.

Examiner insight

When asked to compare devices, you must provide points for both devices and use comparative language, rather than just listing features separately.

Common pitfall

Students often forget to mention specific uses, simply stating 'a mouse is for pointing'. A better answer links the device to a task, such as 'a mouse is used to select icons in a GUI'.

Worked example 14 marks

A graphic designer is creating a company logo. Compare the suitability of using a keyboard and a mouse for this task.

  1. 1

    Step 1: Analyse the task. Creating a logo involves drawing shapes, selecting colours, and possibly adding text.

  2. 2

    Step 2: Evaluate the mouse. A mouse is a pointing device, ideal for navigating the GUI, selecting tools from a palette, clicking on menus, and drawing freeform shapes. It is essential for the graphical aspect of the task.

  3. 3

    Step 3: Evaluate the keyboard. A keyboard is primarily for text entry. It would be used to type the company name if it is part of the logo. Keyboard shortcuts can also speed up workflow (e.g., Ctrl+S to save).

  4. 4

    Step 4: Conclude with a comparison. The mouse is the primary and most suitable device for the drawing and manipulation parts of the task. The keyboard is a necessary secondary device for adding text and using shortcuts, but it cannot perform the main graphical functions.

Recap

  • Keyboards are used for entering text, numbers, and commands.
  • Pointing devices, like a mouse or touchpad, are used to control the cursor in a GUI.
  • A mouse is ideal for tasks like selecting, clicking, and dragging.
  • A touchpad is a common built-in pointing device on laptops.

Quick check

  1. State one advantage and one disadvantage of a touchpad compared to a mouse.2 marks

3. Manual Input: Touch Screens

A touch screen is both an input and an output device. As an input device, it allows users to interact directly with what is displayed on the screen by touching it with a finger or a stylus. There are three main types: Resistive screens (which respond to pressure), Capacitive screens (which detect the electrical charge from a fingertip, common on smartphones), and Infra-red screens (which use a grid of invisible beams). Touch screens are very intuitive and are widely used in smartphones, tablets, information kiosks, and ticket machines.

Key term

Capacitive Screen: A type of touch screen that relies on the electrical properties of the human body to detect where on the display it has been touched.

Examiner insight

Examiners look for context-specific answers. Stating 'it's easy to use' is a weak point; 'it's easy for new users at a train station as it requires no training' is a strong point.

Worked example 14 marks

A train station is installing new ticket machines. Give two advantages and two disadvantages of using touch screens for these machines.

  1. 1

    Step 1: Identify advantages in the context of a public ticket machine. Advantage 1: They are intuitive and easy to use, even for people unfamiliar with computers, as you just touch what you want. This speeds up the queue.

  2. 2

    Step 2: Identify a second advantage. Advantage 2: There are no external peripherals like a mouse or keyboard that could be stolen or damaged, making the machine more robust for public use.

  3. 3

    Step 3: Identify disadvantages in the same context. Disadvantage 1: The screen can become dirty with fingerprints, making it difficult to read. It can also be a hygiene concern.

  4. 4

    Step 4: Identify a second disadvantage. Disadvantage 2: It can be difficult to select small options accurately, which might frustrate some users. Also, bright sunlight can cause glare on the screen, making it hard to see.

Recap

  • A touch screen acts as both an input and output device.
  • Capacitive screens are the most common type in modern personal devices.
  • Advantages include being intuitive to use and saving space (no keyboard/mouse needed).
  • Disadvantages include lack of tactile feedback, screen getting dirty, and difficulty with precise selections.

Quick check

  1. Name the three main types of touch screen technology.3 marks
  2. Why is a capacitive screen not suitable for a user wearing thick gloves?1 mark

4. Direct Data Entry: Scanners & Readers

Direct Data Entry (DDE) devices automate the process of inputting data, making it faster and more accurate than manual entry. Barcode readers use a laser to scan the black and white lines of a barcode, which corresponds to a number in a database. They are used extensively in retail for stock control and at the point of sale. QR (Quick Response) codes are 2D barcodes that can store more information, like a web address or contact details, and are read by cameras on smartphones. Optical Mark Recognition (OMR) detects the position of marks on a pre-printed form, used for multiple-choice exams and lottery tickets. Optical Character Recognition (OCR) converts scanned images of typed or printed text into editable text that a computer can process.

Key term

Direct Data Entry (DDE): A method of entering data into a computer system that does not require manual keying, thus improving speed and accuracy.

Common pitfall

A common mistake is to confuse Optical Mark Recognition (OMR), which sees filled-in boxes, with Optical Character Recognition (OCR), which reads the actual letters and numbers.

Worked example 13 marks

A national examination board needs to process millions of multiple-choice answer sheets.(a) Name the most appropriate DDE device for this task.(b) Explain two benefits of using this device compared to having people mark the sheets manually.

  1. 1

    Step 1:(a) Identify the task. The task is to read marks in specific locations on a pre-printed answer sheet. The most appropriate device for this is an Optical Mark Reader (OMR).

  2. 2

    Step 2:(b) Explain the first benefit. Speed: An OMR scanner can process thousands of sheets per hour, which is vastly faster than a human marker. This allows results to be published much more quickly.

  3. 3

    Step 3:(b) Explain the second benefit. Accuracy: OMR is extremely accurate and removes the possibility of human error in marking (e.g., miscounting scores, getting tired). This ensures fairness and reliability of the results.

Recap

  • DDE devices like scanners and readers enable fast and accurate data input.
  • Barcode readers are used in retail to quickly identify products and look up prices.
  • OMR is used to read the position of marks on a page, such as on multiple-choice exam papers.
  • OCR is used to convert scanned text into an editable digital format.
  • QR codes are 2D barcodes that can store more data, often read by smartphones.

Quick check

  1. What is the main difference between OMR and OCR?2 marks

5. Direct Data Entry: Card & Biometric Readers

These DDE devices are crucial for payments, access control, and identification. Magnetic Stripe Readers read data stored on the black magnetic stripe on the back of a card when it is swiped. This is older, less secure technology. Chip & PIN readers are more secure; the card is inserted into the reader, which reads data from a small microchip. The user must then enter a Personal Identification Number (PIN) to authorise the transaction. Contactless/RFID readers use radio waves to communicate with a chip in the card or a device (like a smartphone) over a short distance, allowing for 'tap-and-go' payments. Biometric readers, such as fingerprint scanners or facial recognition cameras, use unique human characteristics for identification and are a form of DDE.

Key term

RFID (Radio-Frequency Identification): A technology that uses radio waves to read and capture information stored on a tag attached to an object, enabling automatic identification.

Examiner insight

Questions comparing payment methods are very common. High-scoring answers will always discuss data security (encryption), user verification (PIN, signature), and ease of use/speed.

Worked example 14 marks

Compare the security of a payment made using a magnetic stripe reader versus a Chip & PIN reader.

  1. 1

    Step 1: Describe magnetic stripe security. The data on a magnetic stripe is unencrypted and can be easily copied ('skimmed') with simple equipment. If the card is stolen, it can be used without any further verification.

  2. 2

    Step 2: Describe Chip & PIN security. The data on the chip is encrypted, making it much harder to copy. The transaction also requires the user to enter a secret PIN. This provides two-factor authentication: something you have (the card) and something you know (the PIN).

  3. 3

    Step 3: Conclude with a direct comparison. Chip & PIN is significantly more secure because of its use of encryption and the requirement of a PIN. A stolen Chip & PIN card is useless without the PIN, whereas a stolen magnetic stripe card can be used immediately (if only a signature is required).

Recap

  • Magnetic stripe readers are less secure as the data can be easily copied.
  • Chip & PIN readers offer greater security through data encryption and PIN verification.
  • Contactless (RFID) readers allow for fast, low-value transactions by tapping a card or device.
  • Biometric readers use unique personal traits like fingerprints for highly secure identification.

Quick check

  1. Why are contactless payments usually limited to a low transaction value?1 mark

6. Input Devices: Sound & Image Capture

These devices capture real-world analogue data and convert it into a digital format the computer can understand. A microphone is a transducer that converts sound waves (analogue) into electrical signals. These signals are then converted into digital data by an Analogue-to-Digital Converter (ADC), usually on the computer's sound card. This allows for voice recording, voice recognition, and online communication (VoIP). A digital camera (including webcams) works similarly. Its lens focuses light (analogue) onto a sensor (like a CCD or CMOS sensor), which captures the image as a grid of pixels. This digital data can then be stored, edited, and shared.

Key term

Analogue-to-Digital Converter (ADC): A system that converts an analogue signal, such as a sound picked up by a microphone, into a digital signal that can be processed by a computer.

Fun fact

The first photograph ever uploaded to the web in 1992 was of a comedy band called 'Les Horribles Cernettes', made up of female employees at CERN, the European Organization for Nuclear Research.

Worked example 14 marks

Explain the role of a microphone and a webcam in a video conferencing call.

  1. 1

    Step 1: Role of the microphone. The microphone captures the user's voice (analogue sound waves). It converts these waves into an electrical signal, which is then digitised by an ADC.

  2. 2

    Step 2: Role of the webcam. The webcam captures a moving video image of the user. It focuses light onto its sensor, which converts the light into a digital signal representing the image.

  3. 3

    Step 3: Integration. The computer's software combines the digital audio stream from the microphone and the digital video stream from the webcam. This combined data is then compressed and sent over the internet to the other participants in the conference call.

Recap

  • Microphones capture analogue sound waves and convert them to digital data for the computer.
  • Digital cameras and webcams capture analogue light and convert it into a digital image or video.
  • An Analogue-to-Digital Converter (ADC) is essential for converting real-world signals into a format computers can use.
  • These devices are used for VoIP, video conferencing, creating multimedia content, and security.

Quick check

  1. What piece of hardware is responsible for converting the signal from a microphone into a format the CPU can process?1 mark

7. Sensors as Input Devices

A sensor is a special type of input device that automatically measures a physical quantity from the environment and sends the data to a microprocessor. Sensors are the 'senses' of a computer system and are fundamental to monitoring and control systems. The data from a sensor is analogue, so it must be passed through an Analogue-to-Digital Converter (ADC) before the microprocessor can act on it. Common examples include: Temperature sensors (in central heating, greenhouses), Light sensors (to switch on streetlights), Pressure sensors (on a weighing scale, in a burglar alarm), and Infra-red/Motion sensors (in automatic doors, security systems).

Key term

Sensor: A device that detects or measures a physical property and converts it into a signal which can be read by a computer system.

Common pitfall

Students often forget the crucial step of the Analogue-to-Digital Converter (ADC). It's not enough to say 'the sensor sends data to the computer'; you must state that its analogue signal is converted to digital first.

Worked example 14 marks

An automated greenhouse uses sensors to maintain optimal growing conditions for plants. Name two different sensors that would be used and, for each one, describe what it measures and what action the system might take.

  1. 1

    Step 1: Identify the first sensor and its function. Sensor 1: Temperature sensor. This measures the air temperature inside the greenhouse.

  2. 2

    Step 2: Describe the action for the first sensor. If the temperature reading falls below a pre-set value, the microprocessor will send a signal to an actuator to turn on a heater. If it goes above a pre-set value, it will turn on a fan or open a window.

  3. 3

    Step 3: Identify the second sensor and its function. Sensor 2: Moisture/Humidity sensor. This measures the amount of moisture in the soil or the humidity in the air.

  4. 4

    Step 4: Describe the action for the second sensor. If the soil moisture reading falls below a pre-set value, the microprocessor will send a signal to an actuator to turn on a sprinkler system. If the humidity is too high, it might turn on a fan.

Recap

  • Sensors are input devices that measure physical properties from the environment.
  • Sensor data is analogue and must be converted to digital by an ADC.
  • Sensors are key components of computerised control systems.
  • Examples include temperature, light, pressure, and motion sensors.
  • The microprocessor compares sensor data to pre-set values to decide on an action.

Quick check

  1. What type of sensor would be used in a security system to detect an intruder walking past?1 mark

End-of-chapter exercise

Test yourself on the whole chapter. Work through these before moving on.

  1. Define the term 'input device' and give two distinct examples, stating what type of data each one inputs.3 marks
  2. State two advantages of using a barcode reader at a supermarket checkout compared to the cashier typing in codes manually.2 marks
  3. Describe the difference between Optical Mark Recognition (OMR) and Optical Character Recognition (OCR), giving a suitable use for each.4 marks
  4. A bank is upgrading its ATMs. Discuss two advantages and one disadvantage of using a touch screen interface.3 marks
  5. Explain why a Chip and PIN reader provides greater security for a credit card transaction than a magnetic stripe reader.4 marks
  6. A scientist is monitoring conditions in a remote weather station. Suggest three different sensors they might use and state what physical property each sensor would detect.3 marks
  7. Compare and contrast the use of a QR code on a museum exhibit with a printed paragraph of text. Your answer should refer to the amount of data and ease of access.4 marks
  8. Describe the process of recording a person's voice onto a computer. Your answer must mention a microphone, sound card, and Analogue-to-Digital Converter (ADC).5 marks
  9. Explain why Direct Data Entry (DDE) methods are generally faster and less prone to errors than manual data entry.4 marks
  10. A large public library is considering replacing its barcode system for checking books in and out with an RFID system. Evaluate this proposal, considering the advantages and disadvantages for both the library staff and the library users.8 marks

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