By the end of these unit pupils should be able to:
- Identify various input and output devices
Knowledge and Skills
- Effectively work with input/output devices
- Properly install input/output devices to the system unit
Characteristics of input/ouput devices
These devices enable communication between a user and computer.
There are three classifications of Input/ Output devices:
- Those that Send information to the computer
- Those that Display or transmit information from the computer
- Those that Communicate between computers within the network
- Input device - Any device used to enter data into computer is regarded an input device
- Output device - Any device used to display data on or from a computer is regarded an output device
Instructing the computer to perform tasks
A keyboard as an Input device is used to:
- Send information to the computer.
- Input alphanumeric data or instruct computer via series of keystrokes.
Fig.2.1: Desktop Keyboard
Familiarizing with the keyboard keys
Enter key: Executes typed command, performs selected option, marks end of line, or creates blank line.
Back space: Deletes one character to left of flashing cursor; may show as left arrow (!) on the keyboard.
Delete: Deletes character above or to right of flashing cursor.
Spacebar: Inserts blank space between words or sentences.
Escape: Cancels current selection, or generates special code for computer; called Escape key.
Tab: Advances cursor to right by specified number of spaces in word processing program, or to next cell in spreadsheet program.
Shift: Selects uppercase letters for typewriter keys and punctuation symbols on number keys. Can use with other keys to perform function or task.
Caps lock: Locks letter keys to produce only uppercase or lowercase characters.
Control/Ctrl: Provides secondary meaning or function for specific keys.
: Windows key that Displays Start menu.
: Displays shortcut menu similar to right-clicking item. Options in menu depend on where mouse pointer was when key pressed.
Alt: Provides secondary meaning or function for specific keys.
Up/down and left/right arrows: Move cursor up, down, left or right. They are located between typewriter keys and numeric keypad.
Print Scrn: Captures information on screen and sends to Windows Clipboard.
Scroll lock: Toggle (start and stop) scrolling display of data on screen.
Control + Pause: Stop or freeze computer, then continues when any key pressed; sends Break code to computer to unfreeze or unhang computer.
Stop or freeze computer, then continues when any key pressed; sends Break code to computer to unfreeze or unhang computer.
Using the Keyboard
These keys are located along the top row on the keyboard.
They are labeled from F1-F12.
- Each key is assigned a special meaning or function in application programs and operating system installation.
- The Primary purpose of these keys is to provide shortcut for commonly used commands.
Cursor and Numeric Keypad
Can toggle on and off by pressing num lock key
- When on, pad becomes calculator or numeric pad
- When off, pad becomes arrow or cursor movement pad
How to Access the On-Screen Keyboard
To acces the On-Screen Keyboard:
- Click the Start button, then click All Program
- Click Ease of Acces Center, then select On-Screen Keyboard
Using Input or Pointing Devices
Input or pointing devices are devices that instruct a computer through pointing and clicking on a command.
These devices will include the following:
- Touch pad
- Joy stick
A mouse enables you to select or activate items on screen by placing pointer arrow on item and performing the required action such as:
- Moving a mouse on a flat surface causes mouse to initiate movement reflected by pointer on monitor
- Traditional mouse uses ball that rotates to initiate movement as you move mouse device
- Trackball has a ball on one side where your thumb rests while you rotate the ball to move pointer
- Newer mouse models use optical light or diode technology to move pointer on the screen.
Optical Mouse Track Ball Mouse
Fig.2.2: Examples of Mice
Features of a Mouse
Clicking: Point mouse cursor at item, then press left mouse button once and release button to select item.
Double- clicking: Point mouse cursor at item and then click left mouse button twice quickly to initiate programs or open files.
Right- clicking: Point mouse cursor at item and then click right mouse button to display shortcut menu.
Left Drag: Press and hold left mouse button while moving mouse moves items or selects multiple items.
Right Drag: Press and hold right mouse button while moving mouse moves or copies items. When the button is released, shortcut menu appears for further command selection.
Middle wheel/button: Customize to perform certain actions, e.g., use wheel to scroll page up or down.
Thumb button: Customize buttons where thumb rests to perform specific tasks.
Using the Mouse
To select items, grasp the mouse with palm down and index finger gently resting on left button and the middle finger on right button.
- Slide mouse on a flat surface along desk and the mouse pointer moves in same direction on screen
- If run out of space on desk, lift mouse and place in new position on desk, and continue moving
Fig.2.3: Handling a Mouse
To cancel any option, click left button anywhere on screen away from option being selected
Mice are available in traditional style or as wireless devices and can work with PC or Mac computers.
Using touch pad as pointing device
Touchpad is a device that enables you to use a finger to move the pointer.
− It has two buttons that work as left and right mouse buttons
To move the pointer around on screen, place finger on touchpad and glide in direction for pointer to move.
To select item, position pointer over item and then tap touchpad once or click left button.
To activate or launch item, position pointer over item and then tap touchpad twice in quick succession or double-click left button.
To drag an item, position pointer over item, press control and glide finger on touchpad to required location.
To display shortcut menu, position pointer over item and then click right button. A display window will appear.
Touch pad device can work with PC or Mac.
Microphones record sounds and convert into digital format for use internally by the computer.
Voice recognition and conversion is done by use of specialized software that recognizes voice and converts what you say into text characters on screen. This is very beneficial for users with special needs.
This device is not usually included with computer. Students should know that large variety and quality microphones are available for purchase in the market.
Scanners take pictures of original and converts them to digital format for further formatting.
Software (for example OCR) included with scanner determines the degree of details to be captured.
Bar Code Reader
This Scanner is designed to reduce amount of data entry for
routine transactions or verification of product. They are mainly used in super markets.
This device scans or reads thin and thick lines and bar codes from products.
Game Controllers or Joysticks
They are designed to be used with games software.
There are a variety of joysticks available in the market.
This feature is mainly found on mobile phones and i-phones. They use pen or stylus to select or activate items.
Captures pictures and transfer them directly to a computer. The user can view pictures using special cable on computer or television, or print using photo printer. Flash cards can also be used to store more files.
It is a type of digital camera connected to take pictures and video to be shared with others.
- Requires Internet connection and specialized software program
- Some notebooks have built-in Webcam or can be purchased separately
- Can be used to activate commands on projector or while running slideshow
- It also improves accessibility for people with physical impairments
- Biometrics device handle security issues for logon process and to maintain integrity of data on computer
- It require unique identifier before you can access the computer
Looking at Output Devices
Output device enables users to view information the computer displays.
All types of monitors have power switch, brightness and contrast control buttons to adjust screen image.
They are available in variety of sizes, resolutions, and types depending on the resolution, or monitor’s ability to display images.
Thin Film Tube Liquid Cathode Display (TFT LCD) and Cathode Ray Tube (CRT) monitors respectively.
- Measurement is based on particular mathematical levels of sharpness and clarity
- Price factor is also a consideration
Flat screen monitors are very popular due to their sizes as well for touch screen technology.
This device converts digital files into sound using any media player such as Microsoft media player and VLC media player installed in your computer.
There are different forms of sound files:
- Can be specific to music programs or generic for any player device
- File format used to save sound file will determine the quality of that specific audio file
MP3 File Format VLC File Format
Figure 2: Music and Video Files
Optical Mark Recognizer Scanner Magnetic Ink Character Recognizer
OMR, or optical mark recognition, is a technique of electronically recognizing marks in a form, made by a person who is filling up the form. It is useful in automatically processing survey forms of customer feedback forms in large quantities, and then storing the result for later retrieval or for statistical analysis.
OMR is advantageous because it allows you to analyze your forms or questionnaires electronically, thus saving your time and minimizing human error.
Every day, banks process thousands of cheques. It would take them too long to manually enter data from each cheque. Instead, they use a technique called 'Magnetic Ink Character Recognition' (MICR) which enables them to process cheques faster.
At the bottom of each cheque are a series of numbers which record:
- the cheque number
- the bank or cooperative society code
- the customer's account number
These numbers are written in a special ink which contains iron particles. This ink is magnetised the reason for the name 'magnetic ink'. It can be read by a special machine called a Magnetic Ink Character reader (MICR).
The main advantage of MICR
Will only recognise numbers printed in a standard font using the magnetic ink. This provides a high level of security because any attempt to alter the magnetic ink printout with normal ink by writing over it will be ignored.
Set of speakers may be included with computer as separate device to plug in, or may be incorporated into computer.
You can purchase a variety of speakers of different qualities from the market.
Barcode Scanner Barcode Mark
A barcode is a machine-readable optical label that contains information about the item to which it is attached.
Looking at input/out devices
Looking at the mouse