computer lecture 2

8th October8th October 11

INPUT DEVICES

Input devices accept data and instructions from the Input devices accept data and instructions from the user or from another computer system. The keyboard user or from another computer system. The keyboard and mouse are examples of input devices.and mouse are examples of input devices.


TYPES OF INPUT DEVICES

KeyboardKeyboard MouseMouse Punched cardsPunched cards Optical Character Readers (OCR)Optical Character Readers (OCR) Barcode ReaderBarcode Reader PensPens Touch ScreenTouch Screen


KEYBOARD

The Standard Keyboard The Standard Keyboard Layout.Layout.

How a Keyboard Works.How a Keyboard Works.


STANDARD KEYBOARD LAYOUT

A standard computer keyboard has about 100 keys.A standard computer keyboard has about 100 keys.

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


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.


WHAT IS A MOUSE?

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

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


MOUSE TECHNIQUES

Using the mouse involves five techniques:

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

Clicking; Press and release the left mouse button Clicking; Press and release the left mouse button once.once.

Double-clicking; Press and release the left mouse Double-clicking; Press and release the left mouse button twice.button twice.

Dragging; Hold down the left mouse button as you Dragging; Hold down the left mouse button as you move the pointer. move the pointer.

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


VARIANTS OF THE MOUSE

TrackballsTrackballs

TrackpadsTrackpads

Integrated Pointed DevicesIntegrated Pointed Devices


TRACKBALLS

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

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

Many styles of trackball are available.


TRACKPADS

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

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

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


DEVICES FOR THE HAND

PensPens

Touch ScreensTouch Screens

Game ControllersGame Controllers


The user can point, tap, draw and write on the computer’s screen with a pen.


Bar code readers commonly track sales in retail stores


OUTPUT DEVICES

Types of output devicesTypes of output devices MonitorsMonitors PC ProjectorsPC Projectors The most commonly The most commonly

used types of printers used types of printers SpeakersSpeakers


MONITORS

CRT MonitorsCRT Monitors

Flat-Panel MonitorsFlat-Panel Monitors

Comparing MonitorsComparing Monitors

Video ControllersVideo Controllers


PC PROJECTORS

A PC projector connects to a PC and is used to project A PC projector connects to a PC and is used to project images on a large screen.images on a large screen.

Many PC projectors provide the same resolutions and Many PC projectors provide the same resolutions and color levels as high-quality monitors.color levels as high-quality monitors.

Digital light processing (DLP) projectors use a microchip Digital light processing (DLP) projectors use a microchip containing tiny mirrors to produce very sharp, bright containing tiny mirrors to produce very sharp, bright images.images.


Projected Screen


SOUND SYSTEMS SYSTEMS

Multimedia PCs come with a sound card, speakers, and Multimedia PCs come with a sound card, speakers, and a CD-ROM or DVD drive.a CD-ROM or DVD drive.

A sound card translates digital signals into A sound card translates digital signals into analog analog ones that drive the speakers.ones that drive the speakers.

With the right software, you can use your PC to edit With the right software, you can use your PC to edit sounds and create special sound effects.sounds and create special sound effects.


TYPES OF PRINTERS

Dot matrixDot matrix

Ink jet Ink jet

LaserLaser


DOT MATRIXDOT MATRIX

The paper is pressed against a drum (a rubber-coated The paper is pressed against a drum (a rubber-coated cylinder) and is intermittently pulled forward as printing cylinder) and is intermittently pulled forward as printing progresses.progresses.

The electromagnetically-driven print head moves across The electromagnetically-driven print head moves across the paper and strikes the printer ribbon situated between the paper and strikes the printer ribbon situated between the paper and print head pin.the paper and print head pin.

The impact of the print head against the printer ribbon The impact of the print head against the printer ribbon imprints ink dots on the paper which form human-imprints ink dots on the paper which form human-readable characters.readable characters.

It is ideal for environments that frequently print on carbon It is ideal for environments that frequently print on carbon copy.copy.


INKJET PRINTERSINKJET PRINTERS

The relative low cost of the printers and multi-purpose The relative low cost of the printers and multi-purpose printing abilities make it a good choice.printing abilities make it a good choice.

Inkjets use quick-drying, water-based inks and a print Inkjets use quick-drying, water-based inks and a print head with a series of small nozzles that spray ink on the head with a series of small nozzles that spray ink on the surface of the paper. surface of the paper.

The print head assembly is driven by a belt-fed motor The print head assembly is driven by a belt-fed motor that moves the print head across the paper.that moves the print head across the paper.


LASER PRINTERSLASER PRINTERS

Laser printers are known for their high volume output Laser printers are known for their high volume output and low cost-per-page.and low cost-per-page.

Laser printers share much of the same (or similar) Laser printers share much of the same (or similar) technologies as photocopiers.technologies as photocopiers.

Mechanized rollers and gears pull a sheet of paper from Mechanized rollers and gears pull a sheet of paper from a paper tray and through a charge roller, which infuses a paper tray and through a charge roller, which infuses the paper with an electrostatic charge. The paper then the paper with an electrostatic charge. The paper then passes through a printing drum, which is itself inversely passes through a printing drum, which is itself inversely charged and scanned by a laser that emits the print charged and scanned by a laser that emits the print contents across the drum, discharging the drum at points contents across the drum, discharging the drum at points corresponding to text and image points. corresponding to text and image points.

computer lecture 2

Documents

mouse buttons

mouse techniques

left mouse button

right mouse button

mouse trackballs trackpads

input devices input

keyboard controller

keyboard works