Input/Output Devices

• Input/Output devices enable interaction with a computer.

Input-Output Unit

• Input Units get data and programs, preparing them for the computer's processing.
• Input data is provided via devices like keyboards, mice, trackballs, and joysticks and by scanning images and voice/video recording.
• Input devices translate data into a computer-understandable form.
• Output Units receive processed data to make it available to the user via devices such as display screens, printers, plotters, and speakers.

Input Devices

• Input devices can be categorized into:
  • Human Data Entry Devices
  • Source Data Entry Devices

Human Data Entry Devices

• These devices require manual data input, either by typing, keying, or pointing.
• They include:
  • Keyboards
  • Pointing Devices:
    • Mouse
    • Trackball
    • Joystick
    • Digitizing Tablet
  • Pick Devices:
    • Light pen
    • Touch screen

Source Data Entry Devices

• Used for audio and video input to enter source documents directly into the computer.
• They do not require manual typing or pointing.
• They feature:
  • Audio input devices
  • Video input devices
  • Optical input devices:
    • Scanner
    • OCR (Optical Character Recognition)
    • MICR (Magnetic Ink Character Recognition)
    • OMR (Optical Mark Recognition)
    • Barcode Reader

Keyboard

• A common and user-friendly input device.
• Primarily used for text data entry.
• Moves the cursor with typed characters.
• The QWERTY layout is the most prevalent.
• Keyboards often have five sections:
  • Typing keys
  • Numeric keypad
  • Function keys
  • Control keys
  • Special purpose keys
• When a key is pressed, the keyboard interacts with a controller and buffer
• The keyboard controller stores the pressed key's code in the keyboard buffer.
• The computer software reads the keyboard buffer.
• The system software passes the pressed character's code.
• The keyboard buffer stores multiple keystrokes due to the time gap between key presses and the system's reading.

Mouse

• A handheld device with two or three buttons and a scroll wheel.
• The two Types are:
  • Physical
    • Contains a rubber ball that protrudes, requiring a smooth surface for movement.
    • Its rollers and sensors detect the direction and rate of movement.
    • The movement of the rubber ball is sensed by rollers for horizontal and vertical movement and sensors to sense speed, with the data transmitted through a mouse cord.
  • Optical
    • Uses an LED and a sensor to detect movement.
    • Light is reflected when movved.
    • The pulses of light determine the movement's direction and rate, and the data is transmitted through a mouse cord.
    • Introduced by Microsoft in 1999.

Trackball

• It is a variation of the mouse that takes up less space, commonly found in laptops.
• Resembles an upside-down mouse.
• Requires manual rotation of the ball with a finger to move the cursor.
• Remains stationary while the cursor moves in the rotation direction of the ball.
• Its buttons function similarly to a mouse.
• Functions similarly to a physical mouse.

Joystick

• A device mainly for playing video games, especially racing and flying games.
• Controls the cursor's speed
• The direction and amount of stick deflection determine position and speed changes.

Digitizing Tablet

• Used for inputting drawings and sketches and in CAD for building and automobile designs.
• It has two key parts:
  • An electronic tablet
  • A pen with an electronic head.
• Each position on the tablet corresponds to a fixed screen position.
• Contains a circuit detecting pen movement and converting them into digital signals, then sent to the computer.

Light Pen

• A light-sensitive pen used to select objects directly on a computer screen
• Figures/drawings can be created by moving the pen.
• Contains a photocell inside a small tube; light from the screen activates the photocell, transmitting an electric response to the computer to identify the pen's position.

Touch Screen

• Employs an infrared beam grid across the screen's surface.
• Touch breaks the beam, and the location is recorded and sent to the computer.

Audio Input Device

• Used for telephone calls, audio/video conferencing, voice recording, and creating audio files.
• Microphones input voice data.
• Sound cards translate analog audio signals into digital codes and vice versa, enabling Speech/voice recognition that converts spoken words to text.

Video Input Device

• Makes video inputs from video and digital cameras.
• Webcams are a common type.
• A video capture card allows users to connect video input devices.

Optical Input Device - Scanner

• Hand-held and flatbed scanners.

Optical Input Device - OCR (Optical Character Recognition)

• A technique that scans a printed page, translates it, and uses software to recognize the image as editable text.
• OCR uses an Optical Character Reader.
• Editing scanned text requires OCR software.

Optical Input Device - MICR (Magnetic Ink Character Recognition)

• Used in banks to process checks by recognizing magnetic encoding numbers.
• MICR uses a Magnetic Ink Character Reader.
• MICR's reading speed is faster than OCR.
• The numbers at the bottom of checks include the bank, branch, and check numbers.

Optical Input Device - OMR (Optical Mark Recognition)

• Utilized to detect marks on paper using an optical mark reader.
• The reader scans forms and identifies marks positioned correctly, darker than the surrounding paper, and sends this information for processing.
• Employs a reflected beam of light.

Barcode Reader

• Uses adjacent vertical lines of varying widths that are machine-readable, often found in supermarkets and bookstalls.
• Identifies items by reading barcodes with reflective light.
• Inputted to the computer and interpreted by spacing and thickness of the bars.

Output Devices

• Can be divided in to:
  • Hard Copy Devices
  • Soft Copy Devices

Hard Copy Devices

• Output is obtained on paper or any tangible surface, which can be stored permanently, read or used without a computer, and taken anywhere.
• Common examples include printers, plotters, and microfiche.

Printer

• Prints output information onto paper and is used for textual and graphical information.
• Classified into impact and non-impact.
  • Impact
    • Employs a typewriter approach, striking a typeface against paper with an inked ribbon.
    • It is slow.
    • Examples: Dot matrix, daisy wheel, and drum printers.
  • Non-Impact
    • Does not hit or impact a ribbon to print, using electrostatic chemicals and ink-jet technologies.
    • Fast, using electro-static chemicals and ink-jet technologies.
    • Examples: Inkjet and laser printers.

Impact Printer - Dot Matrix

• Print one character at a time.
• Can print alphanumeric characters, special characters, charts and graphs.
• Can only print in black and white.
• Commonly used in payroll and accounting applications.
• Some can print left to right and right to left.

Impact Printer - Daisy Wheel

• Print one character at a time and create letter-quality documents superior to dot matrix printers.
• These printers are slow, print only text (not graphics), and are more expensive than dot matrix printers.
• Suited for high-quality printing where no graphics are needed.

Impact Printer - Drum

• Line printers that are expensive but faster than character printers that generate low-quality output.
• They print 200–2500 lines per minute.

Non-Impact Printer - Ink-jet

• Spray ink directly onto the paper, producing high-quality graphics and text with a resolution exceeding 500 dpi.
• Commonly used in homes and offices.

Non-Impact Printer - Laser

• Provide high-quality text and graphics due to page printers processing and storing the entire page beforehand.
• Offering a rate of 5–24 pages per minute with resolutions ranging from 400 to 1200 dpi.

Plotters

• Used for vector graphics output, such as maps, blueprints of ships, and buildings.
• Plotters use pens of different colors and draw continuous, accurate lines, unlike printers, which create lines from closely spaced dots.
• Are slow and expensive.
• Are of two kinds:
  • Drum plotter: Stationary pens move only horizontally on a carriage over the paper. Movement clock and anti-clockwise, for vertical.
  • Flatbed plotter: Paper is stationary on a flat surface while the pens move horizontally and vertically.
• Primarily used in AUTOCAD, Computer Aided Design (CAD), and Computer Aided Manufacturing (CAM) applications.

Computer Output on Microfilm

• Microfilm is in roll format used to directly record computer output
• A high-speed and low-cost process.
• COM has a much faster data production rate, is used for banking, insurance, medical, and X-ray applications.

Soft Copy Devices

• Soft copy output is obtained in an intangible form through a visual display, audio, or video unit, allowing corrections, storage, and electronic transfer to other users,
• It requires a computer.
• Visual output devices like computer monitors, visual display terminals, video, and audio response systems make it up.

Monitor

• Used to view displayed output alongside the computer.
• The two types:
  • Monochrome
    • Uses one color to display text.
  • Color
    • Displays 256 colors at one time.
• Image depends on Resolution of Screen, Dot Pitch, and Refresh Rate.

Visual Display Terminal

• VDT features a monitor and keyboard together.
• The keyboard inputs data, and the monitor displays computer output.
• There are three terminals:
  • Dumb Terminals
    • No processing and programming capabilities.
  • Smart Terminals
    • Built-in processing capabilities but lacks storage capacity.
  • Intelligent Terminals
    • Built-in processing and storage capacity.

Video Output

• The output device projector displays information from the computer onto a white screen.
• Commonly used for meetings, teaching, conferences, and training.

Audio Response

• A complete sound system consists of a sound card, microphone, speakers, and appropriate software.
• Permits recording, playing, and editing, like cutting and amplification, to make vibrant effects.
• Provides audio output from the computer to the device.
• Speakers, headphones or headsets are used.
• Useful for visually and speech-impaired, helps them read/communicate.