Input Devices

Topic: Input Devices Class: SSS One

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Definition of Input Device

An input device is any hardware component that allows a user to enter data and instructions into a computer. It acts as a bridge, translating human-readable information (like text, clicks, or sounds) into a machine-readable format (binary code) that the computer can understand and process.

Without input devices, a computer would merely be a display screen, unable to interact with users. Data must first be entered into the computer via an input device before any processing can occur.

Some common input devices include:

• Keyboard
• Mouse
• Joystick
• Light Pen
• Trackball
• Scanner
• Graphic Tablet
• Microphone
• Magnetic Ink Character Recognition (MICR) Reader
• Optical Character Recognition (OCR) Reader
• Bar Code Reader
• Optical Mark Recognition (OMR) Reader
• Touchscreen
• Digital Camera
• Webcam
• Stylus

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Keyboard

The keyboard is the most common and widely used input device for entering data into a computer. It looks very similar to electric typewriter keyboards but includes additional keys. Keyboards allow users to input letters, numbers, symbols, and commands into a computer.

Mouse

A mouse is a pointing device that controls the movement of the cursor or pointer on a display screen. It is crucial for graphical user interfaces (GUIs), as it allows users to easily point to options, objects, and click buttons to interact with software.

Touchpad

A touchpad is a small, flat, touch-sensitive surface used as a pointing device, commonly found on portable computers (laptops). By moving a finger across the pad, you can control the pointer's movement on the screen.

Touchscreen

A touchscreen is an electronic visual display that can detect the presence and precise location of a touch within its display area. This allows users to interact directly with what is displayed by touching it with a finger or a stylus.

Trackball

A trackball can be thought of as an upside-down mouse. To move the pointer on the screen, you rotate a ball with your thumb, fingers, or the palm of your hand. A key advantage of a trackball is that it requires very little desk space for operation.

Light Pen

A light pen is a light-sensitive input device shaped like a pen, used in conjunction with a computer's display screen (historically CRT displays). It allows users to point to displayed objects or draw directly on the screen with greater positional accuracy than a finger on a touchscreen. (Note: Light pens are less common with modern display technologies.)

Stylus

A stylus is a small, pen-shaped instrument used to input commands to touchscreens (on mobile devices, tablets, or computer monitors) or to draw on graphics tablets. It provides more precision than a finger.

Joystick and Gamepad

A joystick is an input device consisting of a stick that pivots on a base and reports its angle or direction to the computer. It's primarily used for controlling objects in games, such as navigating a plane in a flight simulator.

A gamepad (also known as a game controller or joypad) is a peripheral device designed to be held in both hands. It features multiple buttons and often one or two mini-joysticks (analog sticks) for controlling characters or actions in video games.

Digital Camera

A digital camera is a camera that captures and stores pictures or video in an electronic format (digital files) directly onto a memory card, rather than on traditional film. These digital files can then be easily transferred to a computer.

Webcam

A webcam is a digital camera connected to a computer, allowing users to capture still images or live video. It's commonly used for video conferencing, online meetings, or broadcasting over the Internet.

Optical Scanner

An optical scanner (commonly called a scanner) is a hardware input device that converts an image or text from a physical document (like a photo or a printed page) into a digital file. This digital file can then be viewed, edited, or stored on a computer.

Barcode Reader

A barcode reader (or barcode scanner) is a hardware device specifically designed to read barcodes. It scans the black and white lines of a barcode and translates them into numerical or alphabetical data, which can then be processed by a computer system, often for inventory management or point-of-sale.

Microphone

A microphone is an audio input device that converts sound waves into electrical signals, which can then be digitized and recorded or processed by a computer. It allows users to input voice commands, record audio, or participate in voice chats.

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Structure and Parts of the Computer Keyboard

A standard computer keyboard is often called a QWERTY keyboard due to the arrangement of the first six keys on the top-left row of its typing area, which resembles that of a traditional typewriter.

Keyboards generally have the following distinct areas:

• Function Keys (F1-F12): These keys are assigned special tasks or functions that vary depending on the software being used.
  • F1: Typically used to get help or open a help menu.
  • F5: Often used for "Find and Replace" or to refresh a web page.
  • F7: Commonly used for spelling and grammar check.
  • F8: Can be used with LCD projector/dual monitor devices.
  • F10: May show Key Tips in Microsoft Office.
  • F12: Often used for "Save As" command.
  Function keys can also be used in combination with other keys like Shift, Alt, and Ctrl.
• Typewriter Keys (Alphanumeric Keys): This is the main section containing letters (A-Z), numbers (0-9), and punctuation keys. Additional important keys include:
  • Spacebar: Separates words or characters.
  • Shift Key: Used to type capital letters or the top symbol on keys.
  • Caps Lock Key: Toggles typing in all capital letters.
  • Enter Key: Used to start a new paragraph in word processors or confirm a selection/command in dialogue boxes.
• Cursor Control Keys (Arrow Keys / Navigation Keys): These keys move your text cursor or navigation pointer in the direction of the arrow. This section also includes:
  • Page Up/Page Down: To scroll quickly through documents or web pages.
  • Home: Moves the cursor to the beginning of a line or document.
  • End: Moves the cursor to the end of a line or document.
• Numeric Keypad: Located on the right side of most full-sized keyboards, it resembles a calculator and is used for quickly entering numbers and performing mathematical operations.
• Combination Keys (Modifier Keys): These keys are used in combination with other keys to perform specific actions.
  1. Shift Key: Used to make capital letters or access alternate characters on keys. Also used in various keyboard shortcuts (e.g., Shift + arrow key to select text).
  2. Alt Key (Alternate Key): Used in combination with other keys for special functions (e.g., Alt + F4 to close an application).
  3. Control Key (Ctrl Key): Widely used in combination with other keys for various shortcuts (e.g., Ctrl + S for Save, Ctrl + C for Copy, Ctrl + V for Paste).
• Other Important Keys:
  • Windows Key: Provides a shortcut to the Start Menu.
  • PrtScn / SysRq (Print Screen): Captures the entire screen. Pressing Alt + PrtScn captures only the currently active window.
  • Esc (Escape): Often used as a shortcut for "No," "Quit," "Exit," "Cancel," or "Abort" in dialogue boxes, and as a stop button in web browsers.
  • Backspace: Erases text to the left of the cursor.
  • Delete: Erases text to the right of the cursor. Also used to delete selected text or files.

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Types of Mouse

1. Mechanical Mouse: This type of mouse contains a rubber or metal ball inside. The movement of the cursor on the screen depends on the movement of this ball. Mechanical mice are typically used on a mouse pad, which is a small, flat pad (often made of rubber or foam) designed to provide smooth movement for the mouse and protect it from dust and dirt.
2. Optical Mouse: Unlike mechanical mice, an optical mouse does not use a ball. Instead, it uses an optical sensor (or a laser) that emits light to detect mouse movement across a surface. Optical mice are generally more precise and less prone to accumulating dirt than mechanical mice. They are more expensive but common today.
3. Wireless Mouse: A wireless or cordless mouse operates without a physical wire connection to the computer. It transmits data using wireless technologies such as radio waves (often via a small USB receiver plugged into the computer) or infrared light waves. This offers greater freedom of movement and reduces cable clutter.

Parts of a Computer Mouse

The specific parts of a computer mouse can vary slightly depending on its type (e.g., mechanical vs. optical, wired vs. wireless). However, below is a general overview of the common parts found on most computer mice:

• Buttons (e.g., left-click, right-click, extra programmable buttons)
• Tracking mechanism (Ball for mechanical, Laser or LED for optical)
• Scroll wheel (for vertical scrolling)
• Circuit board (containing the electronics)
• Connectivity (Cable for wired mouse, or wireless receiver for wireless mouse)

Functions of the Mouse

The primary function of the mouse is to move the mouse cursor (pointer) on the screen. Other important functions include:

1. To Open or Execute a Program: Moving the cursor to an icon, folder, or other object and then clicking or double-clicking that object will open the document or launch the program.
2. To Select: A mouse allows you to select text, a single file, or highlight and select multiple files simultaneously by clicking and dragging.
3. To Drag-and-Drop: Once an item is selected, it can be moved from one location to another by clicking, holding the button, dragging the mouse, and then releasing the button (drag-and-drop method).
4. To Hover: Moving the mouse cursor over objects can reveal additional information or tooltips, helping to discover the function of each object on the screen.
5. To Scroll: When working with long documents or viewing lengthy web pages, you can scroll up or down using the mouse wheel, or by clicking and dragging the scroll bar on the side of the window.

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Differences between Mouse and Keyboard

Keyboard	Mouse
Used primarily to enter text, numbers, and commands.	Used primarily to point, select, and navigate graphically.
Actions are performed by pressing keys.	Actions are performed by clicking buttons or moving the device.
Involves pressing combinations of keys (e.g., Ctrl+C, Alt+F4).	Involves single clicks, double-clicks, or right-clicks.
Cannot directly drag and drop graphical elements.	Allows for dragging and dropping of text, files, and other objects.
Composed of many individual keys.	Typically has 2-3 buttons and a scroll wheel.
Generally does not require a special surface (e.g., works on a desk).	Mechanical and some optical mice often benefit from a mouse pad for smooth operation.