W-6 Comp Hardware

8/14/2019 W-6 Comp Hardware

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PrintersPrinters

A printer is an output devices that produces text and graphics on aphysical 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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PrintersPrinters (Contd)(Contd)

Two categories of printers are Impact Printers

Impact printers use a device to strike an inked ribbon, pressing inkfrom 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 offine wires. The wires strike a ribbon and the paper.


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Printers (Contd)Printers (Contd)

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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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 acceptablequality of print for business letters.


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Laser Printers It is a high speed, high quality printer Laser printers for PCs 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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PrintersPrinters (Contd)(Contd) Laser Printers


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MonitorsMonitors

A monitor is a peripheral device which displayscomputer output on a screen.

Monitors are categorized by the technology theyuse: Cathode ray tube (CRT) Monitors

Flat-panel displays Plasma

Plasma screen technology illuminateslights arranged in a panel-like screen

Type of flat panel display


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Monitors (Contd)Monitors (Contd)

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 electronsat a specially phosphor-coated screen

An electron beam moves back & forthacross the back of the screen.This causes the dots on the front ofthe screen.

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

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

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


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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 gunshoots 3 electrons at the

screen representing theamount of red, green andblue for the pixel


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LCD Flat-Panel Display LCD (Liquid Crystal Display)

A flat-Panel Display Device with a shallow depth that does notuse 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 DevicesMagnetic 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 beneathread/write heads

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


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How Magnetic Storage Works

A magnetic disk's medium contains iron particles, which can be polarizedgivena magnetic chargein 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)

MediumWrite head


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As the mediumrotates, the headwrites the data.

How Magnetic Storage Works (Contd)How Magnetic Storage Works (Contd)


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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 ofthe 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 7200RPM.

Storage capacities of hard disks for personal computers range from 10 GB to320 GB (TB is possible but rare). Read/write heads


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Hard DiskHard Disk (Contd)(Contd)Sectors

each track is dividedinto pie-shapedwedges

ClusterTwo or moresectors combined

TracksData is recorded inconcentric circular bands

The hard disks available today is called an optically assisted hard drives. It combinesoptical technology with magnetic media, which have potential storage capacity up to500 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 formatteda 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 eachfile'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 asquare-shaped plastic shell.

Diskettes come in two sizes: 5.25-inch and 3.5-inch.

Diskettes are available in different capacities, but the most commonstore 1.44 MB.


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Optical Storage DevicesOptical Storage Devices

An optical disc is a high-capacity storage medium. An optical drive usesreflected 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 (Contd)Optical Storage Devices (Contd)

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, portablestorage medium that is usually 4.75 inch in diameter.

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

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

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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A CD-Recordable (CD-R) drive lets you record your own CDs, but datacannot be overwritten once it is recorded to the disk.

A CD-Rewritable (CD-RW) drive lets you record a CD, then write newdata 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 dataenough to store an

entire movie.


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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 slightlydifferent manner and thus it achieves high storage capacity.

HD-DVDs can store 15 GB

Blue-Ray DVDs can store 25 GB

Documents

W-6 Comp Hardware