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Input and Output Devices: A Comprehensive Guide, Lecture notes of Electromechanical Systems and Devices

California Institute of Technology (Caltech)Electromechanical Systems and Devices

A detailed overview of input and output devices used in computer systems. It covers a wide range of devices, including keyboards, mice, touchpads, touch screens, various sensors, magnetic stripe readers, barcode readers, crt monitors, lcd screens, printers, and actuators. Each device is described with its uses, advantages, and disadvantages, offering a comprehensive understanding of their functionalities and applications. Useful for students studying computer hardware and system design, providing a clear and structured explanation of essential concepts. It is suitable for high school and university students, as well as lifelong learners interested in technology. Well-organized and provides a clear explanation of each device, making it easy to understand the concepts.

Typology: Lecture notes

2024/2025

Available from 05/16/2025

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CHAPTER 2 NOTES
Input and Output devices
Input Devices & their Uses
• An input device is any hardware device that allows a user to enter data
or instructions into a computer directly.
• An input device can send data to another device, but it cannot receive
data from another device.
• Input devices are necessary for a computer to receive commands from
its users and data to process; the devices are under the control of the
user or can be direct data entry.
• Input devices can be complicated because they must ensure that the
user can interact with the computer correctly.
Keyboards:
Uses:
• Input of data into applications software
• Typing in commands to the computer
Advantages:
• Fast entry of new text into a document.
• Well-known method.
• Easy to use for most people.
• Easier to do verification checks as data is entered (can immediately
compare the source document with typed data on the screen).
Disadvantages:
• Can be difficult to use if the user has limited arm/wrist use.
• Slow method when compared to direct data entry.
• Fairly large device that uses up valuable desk space.
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CHAPTER 2 NOTES

Input and Output devices

Input Devices & their Uses

  • An input device is any hardware device that allows a user to enter data or instructions into a computer directly.
  • An input device can send data to another device, but it cannot receive data from another device.
  • Input devices are necessary for a computer to receive commands from its users and data to process; the devices are under the control of the user or can be direct data entry.
  • Input devices can be complicated because they must ensure that the user can interact with the computer correctly. Keyboards: Uses:
  • Input of data into applications software
  • Typing in commands to the computer Advantages:
  • Fast entry of new text into a document.
  • Well-known method.
  • Easy to use for most people.
  • Easier to do verification checks as data is entered (can immediately compare the source document with typed data on the screen). Disadvantages:
  • Can be difficult to use if the user has limited arm/wrist use.
  • Slow method when compared to direct data entry.
  • Fairly large device that uses up valuable desk space.

Numeric keypads: Uses:

  • Automatic teller machines (ATMs), where the customer can key in their PIN, amount of money, etc.
  • Mobile phones to allow phone numbers, etc. to be keyed in.
  • Point of sale terminals (POS) in case the barcode reader fails to read the barcode – the number has to be keyed in manually by the operator.
  • Chip and PIN devices when paying by credit/debit cards.
  • Fast entry of numeric data into a spreadsheet. Advantages:
  • Faster than standard keyboards when entering numeric data.
  • Because many are small devices, they are very easy to carry around. Disadvantages:
  • Sometimes have small keys which can make input more difficult.
  • Sometimes the order of the numbers on the keypad is not intuitive. Mouse: Uses:
  • opening, closing and minimizing software
  • grouping, moving and deleting files.
  • image editing, for example, controlling the size and position of a drawing pasted into a document.
  • controlling the position of a pointer on the screen to allow selection. Advantages:
  • Faster method for choosing an option rather than using a keyboard.
  • Very quick way of navigating through applications and the internet.
  • Does not need a large desk area when compared to a keyboard. Disadvantages:
  • Can be more difficult for people with restricted hand/wrist movement than using a keyboard for data entry.
  • Easy to damage, and the older type of mouse quickly becomes clogged up with dirt.
  • Difficult to use if no flat surface readily available. Touchpad:

Disadvantages:

  • Not supplied with the computer as standard, therefore more costly.
  • Users may need training because it is not standard equipment. Remote control: Uses:
  • Televisions, satellite systems, DVD/Blu-ray players and Hi-Fi systems, to alter controls such as volume, on/off etc.
  • Used to control multimedia systems.
  • Used in industrial applications to remotely control processes. Advantages:
  • Can be operated from any reasonable distance.
  • Safer in some conditions, e.g., in chemically hazardous environments, we can control and measure from safe distances. Disadvantages:
  • Difficult to use for people with limited hand/wrist movements.
  • The signal can easily be blocked by physical obstacles. Joysticks: Uses:
  • Used in video games.
  • Used in simulators, to mimic the actual controls. Advantages:
  • Easier than keyboards for screen navigation.
  • In some applications, the control is more realistic than using a mouse. Disadvantages:
  • The on-screen pointer is more difficult to use.

Driving wheel: Uses:

  • Used in video games, especially car racing games.
  • Used in simulators, to mimic actual vehicle controls. Advantages:
  • More realistic experience than both mouse and joystick.
  • Easier than a keyboard or joystick to control steering movements. Disadvantages:
  • Rather expensive input device as compared to a mouse or joystick.
  • Steering movements tend to be over-sensitive, which gives an unrealistic feel.
  • Unless it is an expensive simulator, feedback to steering wheel is non- existent. Touch screen (as an input device): Uses:
  • Automatic teller machines (ATMs) to choose from on-screen options.
  • Point of sale terminals such as in restaurants.
  • Interactive white boards in education.
  • Computer-based training (CBT) where answers are selected during on- screen testing. Advantages:
  • Faster entry of options than using keyboard or mouse.
  • Very easy method for choosing options.
  • User-friendly method – no training necessary in its use.
  • Option to expand the size of the display if necessary. Disadvantages:
  • Limited number of input options available.
  • Can lead to problems if an operator has to use the system frequently (straining of arm muscles, RSI, etc. are all possible).
  • The screen can get very dirty with constant touching. Scanners: Uses:
  • Scanning in documents and converting into different formats
  • Scanning in old documents to protect them, in case original is lost/damaged.
  • Scanning in photographs for storage
  • Scanning in barcodes at POS terminals.

Advantages:

  • Faster to read in text than it is to type it in.
  • Possible to manipulate sound in real time rather than working on a completed recording.
  • Improves security, if used as an authentication system. Disadvantages:
  • Sound files use up a lot of computer memory.
  • Reading in data is more error prone than typing in. Sensors: Uses:
  • Temperature sensors are used in automatic washing machines, central heating systems, ovens, automatic glasshouses.
  • Pressure sensors are used in intruder alarm systems, washing machines.
  • Light sensors are used in automatic glasshouses, automatic doors, street lighting control.
  • Sound/acoustic sensors are used in intruder alarm systems, monitoring liquid and powder flow in pipes.
  • Humidity/moisture sensors are used in automatic glasshouses, environmental monitoring, in factories where moisture levels are crucial.
  • pH sensors are used in automatic glasshouses, chemical processes and environmental monitoring. Advantages:
  • Readings are more accurate as compared to human operators.
  • Readers are continuous, no breaks in the monitoring.
  • Because it is a continuous process, any action or warnings needed will be initiated immediately.
  • Automatic systems don’t need human intervention. Disadvantages:
  • Faulty sensors can give spurious results.
  • Most sensors are analogue; therefore, they require conversion using Analogue to Digital Convertors. Light pens: Uses:
  • Selecting object on CRT screens
  • Drawing on screens

Advantages:

  • Greater accuracy than touch screens
  • Small, makes them portable as well as capable of being used in small spaces.
  • Easy-to-use technology. Disadvantages:
  • Lagging problems while drawing on screen.
  • Only works with CRT monitors.
  • Rather dated technology.
  • Easy to hack into the signal.
  • RFID is more expensive than a comparable barcode system. Optical Mark Reader/Recognition (OMR): Uses:
  • Used in MCQs checking.
  • Used in reading voting papers. Advantages:
  • Very fast way of inputting survey results.
  • More accurate because there is no human intervention.
  • More accurate than OCR methods. Disadvantages:
  • The designing of the forms can be complicated to make sure the marks are correctly positioned.
  • If there are problems, they need to be manually checked, which can be time-consuming. Optical Character Recognition/Reader: Uses:
  • Processing passports and identity cards.
  • Converting hard copy documents into electronic form.
  • Used in automatic number plate recognition (ANPR) systems.
  • Digitizing historic hard copies for archiving. Advantages:
  • Much faster data entry system than manual typing.
  • No human intervention, its error free. Disadvantages:
  • System has difficulty in reading different handwritings.
  • Still not a very accurate technique. Barcode readers: Uses:
  • Used in supermarkets for stock control.
  • In libraries, to keep track of books.
  • As a safety function to ensure checking of electrical equipment on a daily basis. Advantages:
  • Much faster than manually keying in data.
  • Allow automatic stock control.
  • They are a tried and trusted technology.

Disadvantages:

  • Relatively expensive system to administer.
  • Not fool-proof, barcodes can be swapped between items.
  • Can be more easily damaged than RFID tags or magnetic stripes. Quick response (QR) code scanner: Uses:
  • used in advertising to contain information about the advertising company.
  • Wi-Fi authentication
  • Used in restaurants, you can see the menu by scanning. Advantages:
  • hold much more information than normal barcode.
  • fewer errors than with barcodes.
  • QR codes are easier to read because they can even be read by the cameras on a smartphone.
  • It is possible to encrypt QR codes. Disadvantages:
  • More than one QR format is available.
  • QR codes can be used to transmit malicious data.

Disadvantages:

  • They tend to get dirty with frequent use.
  • Frequent use results in straining of arm muscles, RSI, etc.
  • If large amounts of data are being input/output, they aren’t very accurate, and the interface isn’t very fast. Multimedia projectors: Uses:
  • Training presentations to allow whole audience to see images.
  • Advertising presentations.
  • Home cinema systems. Advantages:
  • More people can watch as they don’t have to crowd around a laptop.
  • Avoids the need for several networked computers. Disadvantages:
  • Images can be fuzzy.
  • Expensive to buy.
  • Set-up can be complicated. Laser printers: Uses:
  • In uses where low noise is required.
  • If fast, high quality, high-volume printing is required. Advantages:
  • Printing is fast.
  • They can handle very large print jobs.
  • Quality is consistently high.
  • Toner cartridges last for a long time. Disadvantages:
  • They are only considerably fast if several copies are being made.
  • Color laser printers are expensive to run.
  • They produce ozone and volatile organic compounds because of their printing method and toner.

Inkjet printers: Uses:

  • Where low-output volumes are required.
  • Where high-quality printing is required for single pages. Advantages:
  • High-quality output
  • Cheaper than laser printers.
  • Very lightweight
  • Don’t produce ozone and volatile organic compounds. Disadvantages:
  • Slow output if many copies are needed.
  • Can’t do large print jobs.
  • Printing can smudge if user isn’t careful.
  • Can be expensive if used a lot. Dot matrix printers: Uses:
  • Used in environments where noise isn’t a major issue.
  • Carbon copies or multi-part outputs can be produced.
  • Widely used in till receipts. Advantages:
  • Can be used in varying environments unlike laser/inkjet printers.
  • Carbon copies or multi-part outputs can be produced.
  • Very cheap to run and maintain.
  • Good for continuous printing. Disadvantages:
  • Very noisy
  • Initial cost is more than an inkjet printer.
  • Very slow, poor-quality printing.

Speaker: Uses:

  • Used in all phones and most computers.
  • Helps visually impaired people.
  • Plays downloaded sound files. Advantages:
  • Amplified sounds can be much louder than the original sound.
  • Amplified sounds can be enough to be heard by a huge crowd.
  • Very simple technology.
  • They are especially useful for blind people, for instance, reading e-books. Disadvantages:
  • Speaker output can be disturbing to irrelevant people present in the same area, e.g., an office.
  • Sound quality is high only in expensive speakers.
  • They take up a lot of desk space. Actuators: Uses:
  • Used to turn on motors, buzzer, switches.
  • Allow a computer to control physical devices, Advantages:
  • Allow remote operation of many devices.
  • Relatively inexpensive devices. Disadvantages:
  • They are an addition device in the system that could go wrong.
  • As they are analogue devices, signals need to be converted using a DAC.