Lecture # 3

Revision Of Lec # 2Standard Input Methods

Assignment # 2

Revision

• What is a Computer?

• Data and its Types

• Parts Of Computing

• Parts Of Computer

• Processor

• Memory

Revision

• Information

• I\O Devices

• Storage

• Types Of Storage

• Difference B\w Storage and Memory

• Categories Of Computers

Standard Methods of Input

This lecture includes the following sections:

The Keyboard

The Mouse

Variants of the Mouse

Devices for the Hand

Optical Input Devices

Audio-Video Input Devices

• The Standard Keyboard Layout

• Ergonomic Keyboards

• Variants Of Keyboard

• How a Keyboard Works

Theeyboard

The Keyboard

• It is an input device.

• Its design came from typewriters that did not use electricity.

• A person can type a document, access menus, play games and perform variety of other tasks.

The Keyboard

• Keys, called Keycaps are the same size and shape from keyboard to keyboard.

• These are also placed at the similar distance from one another in a similar pattern.

• A standard computer keyboard has about 100 keys.

• Most keyboards use the QWERTY layout, named for the first six keys in the top row of letters.

The Keyboard - Standard Keyboard Layout

5. Cursor-movement keys

4. Modifier keys

3. Function keys

2. Numeric keypad

1. Alphanumeric keys

Most keyboards have keys arranged in five groups:

The Keyboard - Standard Keyboard Layout

ACADEMIC RECORDS

Password

Invalid Password

* * * * *

• Long periods of keyboard use can cause injuries.

• An ergonomically correct keyboard can help you avoid injuries.

• This design keep a user’s hands stay positioned correctly, reducing bending and strain.

• These look like traditional keyboard, but been divided down the middle, keeping a person’s hands farther apart and aligning the wrists with the forearms.

The Keyboard - Ergonomic Keyboards

Variants of Keyboard

• Das Keyboard:

• Completely black keyboard with weighted keys • These weighted keys require more pressure from a

person's strongest fingers and less pressure from the weaker ones.

• True-touch Roll-up keyboard:

• Flexible and can be rolled up to fit in a backpack or bag.

Variants of Keyboard

• Illuminated keyboards:

• It uses light-emitting diodes or electroluminescent film

to send light through the keys or the spaces between keys.

• Optimus keyboard:

• It has organic light-emitting diodes (OLEDs) in the keys.

• Users can change what letter, command or action each key

represents, and the OLED can change to display the new

information.

The Keyboard - How a Keyboard Works

• A keyboard is a lot like a miniature computer.

• It has its own processor and circuitry that carries information to and from that processor.

• A large part of this circuitry makes up the key matrix.

Key Matrix

Parts of Keyboard Circuitry

• Keyboard controller

• Keyboard buffer

• Scan code

• Interrupt request

• The keyboard controller detects the keystroke.

• The controller places a scan code in the keyboard buffer, indicating which key was pressed.

• The keyboard sends the computer an interrupt request, telling the CPU to accept the keystroke.

When you press a key:

The Keyboard - How a Keyboard Works

How the Computer Accepts Input from the Keyboard

• Keyboard controller• Keyboard buffer• Scan code• Interrupt request• Repeat rate

The Mouse

• What is a Mouse?

• Mouse Techniques

The Mouse - What is a Mouse?

• The mouse is a pointing device. You use it to move a graphical pointer on the screen.

• The mouse can be used to issue commands, draw, and perform other types of input tasks.

The Mouse - Mouse Techniques

1. Pointing; Move the mouse to move the on-screen pointer.

2. Clicking; Press and release the left mouse buttononce.

3. Double-clicking; Press and release the left mousebutton twice.

4. Dragging; Hold down the left mouse button as youmove the pointer.

5. Right-clicking; Press and release the right mouse button.

Using the mouse involves five techniques:

Variants of the Mouse

• Trackballs

• Trackpads

• Integrated Pointed Devices

Variants of the Mouse - Trackballs

• A trackball is like a mouse turned upside-down.

• Use your thumb to move the exposed ball and your fingers to press the buttons.

Many styles of trackball are available.

Variants of the Mouse - Trackpads

• A trackpad is a touch-sensitive pad that provides the same functionality as a mouse.

• To use a trackpad, you glide your finger across its surface.

• Trackpads provide a set of buttons that function like mouse buttons.

Variants of the Mouse-Integrated Pointing Devices

• An integrated pointing device is a small joystick built into the keyboard.

• To use an integrated pointing device, you move the joystick.

• These devices provide a set of buttons that function like mouse buttons

Alternative MethodsOf Input

Input Devices for the Hand

• Pen, sometimes called a stylus

• Touch screen• Game controller

Devices for the Hand - Pens

• With a pen-based system, you use an electronic pen to write on the screen and choose commands.

• Pens are common input devices for handheld computers, like “personal digital assistants (PDAs).”

• Pens are handy for making notes or selecting commands, not for inputting a lot of text.

The user can point, tap, draw and write on the

computer’s screen with a pen.

Devices for the Hand - Touch Screens

• Touch-screen systems accept input directly through the monitor.

• Touch screens use sensors to detect the touch of a finger. They are useful where environmental conditions prohibit the use of a keyboard or mouse.

• Touch-screen systems are useful for selecting options from menus.

Devices for the Hand - Game Controllers

• The two primary types of game controllers are joysticks and game pads.

• Game pads is a small, flat device that usually provides two sets of controls one for each hand.

• Joysticks are popular for flight simulator and driving games.

Optical Input Devices

• Bar code reader• Image scanner and

optical character recognition (OCR)

Optical Input Devices - Bar Code Readers

• Bar code readers can read bar codes—patterns of printed bars.

• The reader emits light, which reflects off the bar code and into a detector in the reader. The detector translates the code into numbers.

• Flatbed bar code readers are commonly found in supermarkets. Courier services often use handheld readers.

Bar code readers commonly track

sales in retail stores

Optical Input Devices –Image Scanners and OCR

• Image scanners digitize printed images for storage and manipulation in a computer.

• A scanner shines light onto the image and interprets the reflection.

• Optical character recognition (OCR) software translates scanned text into editable electronic documents.

OCR

• The basic principle of a scanner is to analyze an image and process it in some way.

• Image and text capture (optical character recognition or OCR) allow you to save information to a file on your computer.

• You can then alter or enhance the image, print it out

Parts Of Scanner• Charge-coupled device (CCD) array • Mirrors • Scan head • Glass plate • Lamp • Lens • Cover • Filters • Stepper motor • Stabilizer bar • Belt • Power supply • Interface ports) • Control circuitry

Working

• The core component of the scanner is the CCD array.• CCD is the most common technology for image

capture in scanners. • CCD is a collection of tiny light-sensitive diodes,

which convert photons (light) into electrons (electrical charge). These diodes are called photosites.

• Each photosite is sensitive to light -- the brighter the light that hits a single photosite, the greater the electrical charge that will accumulate at that site.

Light source, lensand diode array

Documentbeing

scanned

Convertsdiode signalsto numbers

To computer

Types Of Scanner

• Flatbed scanners also called desktop scanners, are the most versatile and commonly used scanners.

• Sheet-fed scanners are similar to flatbed scanners except the document is moved and the scan head is immobile. A sheet-fed scanner looks a lot like a small portable printer.

• Handheld scanners use the same basic technology as a flatbed scanner, but rely on the user to move them . This type of scanner typically does not provide good image quality. However, it can be useful for quickly capturing text.

Audio-Visual (Multimedia) Input Devices

• Microphones and Speech Recognition Software

• Video Input

• Digital Cameras

Audio-Visual (Multimedia) Input Devices - Microphones and Speech Recognition

• Microphones can accept auditory input. A microphone requires a sound card in the PC.

• A sound card can digitize analog sound signals, and convert digital sound signals to analog form.

• With speech recognition software, you can use your microphone to dictate text, navigate programs, and choose commands.

Digital Audio Output[electrical signals]

(ex. 11100011) tocomputer

Analog Sound Signals

Analog Signals are Digitized

Audio-Visual (Multimedia) Input Devices – Video Input

• PC video cameras digitize full-motion images.

• Digital cameras capture still images.

• These cameras break images into pixels and store data about each pixel.

• Video images may be compressed to use less memory and storage space.

Assignment # 2

• Discuss in detail optical Input Devices, explain the working of them.

• Discuss in detail Audio-Video Input Devices and their working.