Week-5Week-5 Output Devices Printing Devices

Impact PrintersNon-Impact Printers

Display Devices Monitors LCD Plasma

Storage DevicesMagnetic Storage DevicesOptical Storage Devices

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PrintersPrinters A printer is an output devices that produces text and graphics on

a physical medium such as paper or transparencies. A printer often connects by a cable to a parallel port or a USB

port. There are different printers with varying speeds, capabilities and

printing methods.

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Printers Printers (Cont’d)(Cont’d)

Two categories of printers are Impact Printers

Impact printers use a device to strike an inked ribbon, pressing ink from the ribbon onto the paper.

Impact printer is noisy because of striking mechanism. e.g. Dot matrix printers

Dot matrix printers produce characters and graphics by using a grid of fine wires. The wires strike a ribbon and the paper.

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Printers (Cont’d)Printers (Cont’d) Non-Impact Printers

Non-impact printers form characters & graphics on a piece of paper, without actually striking on paper.

Some spray ink while other use heat or pressure to create images.

These printers are much quieter than the impact printers.

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Printers (Cont’d)Printers (Cont’d) Commonly used non-impact printers are

Ink-jet Printers It is a type of non-impact printer that form characters & graphics by

spraying tiny drops of liquid ink on a paper. The most popular type of color printers for use in offices or home

because of their low cost & letter-quality print, which is an acceptable quality of print for business letters.

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Printers (Cont’d)Printers (Cont’d) Laser Printers

It is a high speed, high quality printer Laser printers for PC’s ordinarily more removable trays that

slides into the printer case. Laser printers are available for color and black-and-white

printing. Quality determined by dots per inch (dpi) produced Expensive initial costs but cheaper to operate per page

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Printers Printers (Cont’d)(Cont’d)

Laser Printers

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MonitorsMonitors A monitor is a peripheral device which displays computer output on a screen. Monitors are categorized by the technology

they use: Cathode ray tube (CRT) Monitors Flat-panel displays Plasma

Plasma screen technology illuminates lights arranged in a panel-like screen Type of flat panel display

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Monitors (Cont’d)Monitors (Cont’d) CRT (Cathode Ray Tube)

A CRT is a large, sealed glass tube, the front of a tube is a screen. Electron gun shoots a stream of electrons

at a specially phosphor-coated screen An electron beam moves back & forth

across the back of the screen. This causes the dots on the front of the screen.

The dots are grouped into pixels, which glow when struck by electrons.

In color CRTs, each pixel contains a red, green, and blue dot. These glow at varying intensities to produce color images.

CRT monitors for desktop computers are available in various size, with the more common being 15, 17, 19, 21 inches etc …

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Monitors (Cont’d)Monitors (Cont’d)

PixEL (Picture Element) smallest unit of an image, basically a single dot on the screen

Resolution Number of pixels in the image Common resolution size is 1024x768

The CRT electron gun “shoots” 3 electrons at the screen representing the amount of red, green and blue for the pixel

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Monitors (Cont’d)Monitors (Cont’d) LCD Flat-Panel Display

LCD (Liquid Crystal Display) A flat-Panel Display Device with a shallow depth that does

not use CRT technology. Forms output by solidifying crystals and “backlighting” the

image with a light source TV sets are CRTs and many desktop monitors use this

technology LCD is primarily used for laptops and other portable devices

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Storage DevicesStorage Devices Storage devices holds data, instructions & information for future

use. Every computer uses storage devices to holds software,

specifically system software & application software's. It is also called Secondary Storage or Auxiliary Storage Devices. Example of storage media are Magnetic Storage Devices

Hard Disk, Floppy Disk

Optical Discs: CD-R, CD-RW, DVD

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Magnetic Storage Devices Magnetic Storage Devices Exploits duality of magnetism and electricity

Converts electrical signals into magnetic charges Captures magnetic charge on a storage medium Later regenerates electrical current from stored magnetic

charge Polarity of magnetic charge represents bit values zero and one

Flat, circular platter with metallic coating that is rotated beneath read/write heads

Random access device; read/write head can be moved to any location on the platter

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How Magnetic Storage Works A magnetic disk's medium contains iron particles, which can be polarized

—given a magnetic charge—in one of two directions. Each particle's direction represents a 1 (on) or 0 (off), representing each

bit of data that the CPU can recognize. A disk drive uses read/write heads containing electromagnets to create

magnetic charges on the medium.

Random particles(no data stored)

Current flow(write

operation)

Organized particles(represent data)

Medium

Write head

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As the mediumrotates, the headwrites the data.

How Magnetic Storage Works How Magnetic Storage Works (Cont’d)(Cont’d)

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Magnetic Storage Devices - Disk AreasMagnetic Storage Devices - Disk Areas

When a disk is formatted, the OS creates four areas on its surface: Boot sector – stores the master boot record, a small program that runs

when you first start (boot) the computer File allocation table (FAT) – a log that records each file's location and

each sector's status Root folder – enables the user to store data on the disk in a logical way Data area – the portion of the disk that actually holds data

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Hard DisksHard Disks

Auxiliary storage is a hard disk. Hard disks use multiple platters, stacked on a spindle. or A hard disk consists of one or more rigid metal plates coated with a

metal oxide material that allows data to be magnetically recorded on the surface of the platters.

Each platter has two read/write heads, one for each side. The hard disk platters spin at a high rate of speed, typically 5400 to

7200 RPM. Storage capacities of hard disks for personal computers range from 10

GB to 320 GB (TB is possible but rare). Read/write heads

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Hard Disk Hard Disk (Cont’d)(Cont’d)

Sectorseach track is divided into pie-shaped wedges

ClusterTwo or more sectors combined

TracksData is recorded in concentric circular bands

The hard disks available today is called an optically assisted hard drives. It combines optical technology with magnetic media, which have potential storage capacity up to 500 GB.

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FormattingFormatting

Formatting is the process of preparing a disk for reading and writing. Before a magnetic disk can be used, it must be formatted—a process

that maps the disk's surface and determines how data will be stored. During formatting, the drive creates circular tracks around the disk's

surface, then divides each track into sectors. The OS organizes sectors into groups, called clusters, then tracks

each file's location according to the clusters it occupies.

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Floppy DiskFloppy Disk It is also called Diskette. It is portable, inexpensive storage medium that consist of thin,

circular, flexible plastic film with a magnetic coating enclosed in a square-shaped plastic shell.

Diskettes come in two sizes: 5.25-inch and 3.5-inch. Diskettes are available in different capacities, but the most

common store 1.44 MB.

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Optical Storage DevicesOptical Storage Devices An optical disc is a high-capacity storage medium. An optical drive uses

reflected light to read data. To store data, the disc's metal surface is covered with tiny dents (pits)

and flat spots (lands), which cause light to be reflected differently. When an optical drive shines light into a pit, the light cannot be

reflected back. This represents a bit value of 0 (off). A land reflects light back to its source, representing a bit value of 1 (on).

01

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Optical Storage Devices (Cont’d)Optical Storage Devices (Cont’d) CD's (Compact Disc) 700 MB storage

CD-ROM (read only) CD-R: (Record) to a CD CD-RW: Can write and erase CD to reuse it (Re-Writable) DVD (Digital Video Disc)

A compact disk (CD), also called an optical disc, is a flat round, portable storage medium that is usually 4.75 inch in diameter.

A CD-ROM (read only memory), is a compact disc that used the same laser technology as audio CDs for recording music.

In addition it can contain other types of data such as text, graphics, and video.

The capacity of a CD-ROM is 650 MB of data, about 70 minutes of audio.

Once data is written to a standard CD-ROM disk, the data cannot be altered or overwritten.

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Optical Storage Devices (Cont’d)Optical Storage Devices (Cont’d) A CD-Recordable (CD-R) drive lets you record your own CDs, but

data cannot be overwritten once it is recorded to the disk. A CD-Rewritable (CD-RW) drive lets you record a CD, then write

new data over the already recorded data. A variation of CD-ROM is called Digital Video Disk Read-Only

Memory (DVD-ROM), and is being used in place of CD-ROM in many newer PCs.

Standard DVD disks store up to 4.7 GB of data—enough to store an entire movie.

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Optical Storage Devices (Cont’d)Optical Storage Devices (Cont’d) Dual-layer DVD disks can store up to 9.4 GB. DVD disks can store so much data because of sophisticated data

compression technologies. At a glance, a DVD-ROM look like a CD-ROM, the size and shape

are similar, but DVD-ROM store data, instructions & information in a slightly

different manner and thus it achieves high storage capacity.

HD-DVDs can store 15 GB

Blue-Ray DVDs can store 25 GB