INPUT DEVICES - Notes.

Standard Methods of Input

This Topic includes the following sections:
· The Keyboard
· The Mouse
· Variants of the Mouse

The Keyboard

•The Standard Keyboard Layout
• Ergonomic Keyboards
• How a Keyboard Works

The Keyboard - Standard Keyboard Layout

•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

Most keyboards have keys arranged in five groups:


1. Alphanumeric keys

2. Numeric keypad

3. Function keys

4. Modifier keys
5. Cursor-movement keys

Ergonomic Keyboards

•Ergonomics->Study of Physical relationship between people and their tools.
•Long periods of keyboard use can cause injuries.
•An ergonomically correct keyboard can help you avoid repetitive stress (strain) injuries (RSI).
•You also can avoid injuries by adopting correct keyboarding practices.

The Keyboard - How a Keyboard Works

When you press a key:

•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.

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.

Variants of the Mouse

•Trackballs
•Trackpads
•Integrated Pointed Devices

Types of Mouse

1.Mechanical Mouse
2.Optical Mouse (Non mechanical)

Mouse Function (Mechanical)

Mouse movesà Mouse ball spins the rollerà Roller gives information to the system softwareà System software controls the pointer

Mouse Function (Optical)

Mouse emits a beam of light-> From the Reflected light distance, direction and speed of pointer is evaluated-> System software controls the pointer

The Mouse - Mouse Techniques


Using the mouse involves five techniques:

1.Pointing; Move the mouse to move the on-screen pointer.
2.Clicking; Press and release the left mouse button
once.
3.Double-clicking; Press and release the left mouse
button twice.
4.Dragging; Hold down the left mouse button as you
move the pointer.
5.Right-clicking; Press and release the right mouse button.

Variants of the Mouse - Trackballs

•A trackball is like a mouse turned upside-down & needs less working space.
•Use your thumb to move the exposed ball and your fingers to press the buttons.

Track pads

•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.

Integrated Pointing Devices

•An integrated pointing device is a small joystick built into the keyboard between G and H.
•To use an integrated pointing device, you move the joystick.
•These devices provide a set of buttons that function like mouse buttons

Alternative Input Devices –
Devices for the Hand

• Pens
• Touch Screens
• Game Controllers

Devices for the Hand - Pens

•With a pen-based system, you use an electronic pen called as stylus to write on the screen and choose commands.
•Pens are common input devices for handheld computers, like personal digital assistants (PDAs) and tablet PC for collecting database
•Pens are handy for making notes or selecting commands, not for inputting a lot of text.

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.
•They are useful for ATM, information centre like railways, departmental stores etc.

Devices for the Hand - Game Controllers

•Game controller is an input device which accepts i/p from the user, process it, and produce o/p in the form of graphics and sound
•The two primary types of game controllers are joysticks and game pads.
•Game pads usually provide controls for each hand. They are flexible and used to control games
•Joysticks are popular for flight simulator and driving games. Some type includes steering wheel, gearshifts and foot pedals


Alternative Input Devices –
Optical Input Devices


•Bar Code Readers
•Image Scanners and OCR (Optical Character Recognition)

Optical Input Devices - Bar Code Readers

•Bar code readers can read bar codes—patterns of printed bars to identify the product.
•The reader emits light, which reflects off the bar code.
A light sensitive detector identifies the bar code image by recognizing special bars at both ends of the image.
•They tells the reader whether the barcode has been read right side up or upside down. Then it converts the individual bar patterns into corresponding code. Then the reader feeds the data into the computer.
•Flatbed bar code readers are commonly found in library, supermarkets. Courier services often use handheld readers.

Optical Input Devices :Image Scanners and OCR

•Image scanner convert any printed image into electronic form by shining light onto the image and sensing the intensity of light reflection at every point.
•Thus they digitize printed images for storage and
manipulation in a computer.
•Color scanners use filters to separate the components of color into the primary additive color (RGB)
•After scanning, when it is a photo we can use photo shop application to change the properties of picture like adjusting contrast, changing color etc.

•Scanners come in a range of size from hand held model to flat bed scanners that sit on desktop.`
•Hand held scanners or portable but require multiple passes to scan a single page because they are not wide as paper.
•Flat bed scanners offered high quality reproduction since it can scan a page in single pass (Xerox m/c).
•Some medium sized scanners are also available (FAX m/c).

OCR
•When it is a text document we can use Optical character recognition (OCR) software to translate scanned text into editable electronic documents.
•Image is first stored as bit map. A bit map is grid of dots, each dot is represented by one or more bits.
•OCR translate the array of dots into letters and numbers.
•For that, it looks at each character and tries to match the character with its own assumption. OCR extremely complex and not 100% accurate.
•It is used to convert the fax into editable document.

Alternative Input Devices –
Audio-Visual (Multimedia) Input Devices

• Audio input àMicrophones and Speech Recognition
• Video Input àPC video camera, Digital camera

Microphones and Speech Recognition

•Microphones can accept auditory input. A microphone requires a sound card in the PC.
•A sound card is a special device which translate analog sound signal from the microphone into digital codes the computer can store and process .This process is called digitizing. Vice-versa can also be done by sound card.
•By this we can record our voice and store it as file in computer. We can use it in presentations, webpages or email it to others.
•With speech recognition software (voice recognition), you can use your microphone to dictate text, navigate programs, and choose commands.

•SRS takes the smallest individual sound in a language called phonemes, and translate them into text.
•Some problem occurs are
1.Differentiating sound for eg: during the process of two and too.
2. To isolate background noise.
3. Need of pause between words.
• Newer software overcome these problems by training with speech patterns and pronunciation.
•Other types of audio i/p are CD, tape player, radio…
MIDI-Musical Instrument Digital interface
A MIDI port or adapter is used to connect the musical instruments to computer.

Video Input

•Applications like video conferencing and video chat needs video files to be communicated between computers.
•PC video cameras digitize full-motion images and can transmit them in n/w. eg:webcam
•It breaks images into pixels and each pixel’s color and characteristics are stored as digital code.
•Video capture card is used to connect video devices to PC.
•Digital cameras are portable, handheld device that capture still images.
•Difference between normal film camera and digital camera.
•Video images may be compressed to use less memory and storage space for passing in network.