MATH101NUMERICAL &

IT LITERACYLecture 2:

Secondary Storage, Input and Output Devices

Dr Yingchao ZHAO

LECTURE OUTCOMES After this lecture, you should be able to:

Describe the different types of secondary storage devices

Be aware of the existence of different input devices and their basic mechanisms.

Be aware of the existence of different output devices and their basic mechanisms.

SECONDARY STORAGE

STORAGE Storage holds data, instructions, and

information for future use. Storage medium is the physical material

on which a computer keeps data, instructions, and information.

Two key areas in evaluating storage systems:CapacityAccess time

STORAGE SYSTEMS

CAPACITY Capacity is the number of bytes a

storage medium can hold.This shows

common units for counting

size.

From Wikipedia

CAPACITY What can be stored in 1TB space?

500,000,000 pages of text285,000 digital photos250,000 songs120 hours of digital video

HARD DISKS One of the most

popular secondary storage.

Mainly magnetic disks. Properties:

Random access – at any time, any part on HD can be accessed.

High capacity – up to TB Medium access time (several

ms) – ~100000 times slower than RAM, ~100 times faster than DVD.

Data stored on hard disks are first loaded into RAM before being processed or displayed.

HARD DISKS – PRECAUTION A head crash occurs when a read/write

head touches the surface of a platter.E.g., when something happened suddenly

(power off, detach, fall down, etc.) during read/write.

Read/write head is really close to the

platters!

Always backup your hard disk!

HARD DISKS – RECOVERY If a HD crashes, data inside it cannot be

retrieved by normal OS. Recovery is costly!

> $1000 for simple cases and >$10000 for more complex cases

Recovery of data is not guaranteed. Imagine the case where the read/write head

scratched a portion of disk platter. No way to recover the data stored inside.

HARD DISKS – FORMAT Hard disks must be formatted before

useThe OS can then read/write files on the

disks. Different OSes format disks to different

formats, e.g.,FAT32 / NTFS for Windowsext4 for Linux / UNIXHFS+ for MacOS

New HDs are usually formatted before put on shelves.

RAID AND NAS RAID (redundant array of independent

(inexpensive) disks) is a group of two or more integrated hard disks.Data are duplicated automatically.Data can be recovered even if one HD fails.Faster read access.

A network attached storage (NAS) device is a server connected to a network with the sole purpose of providing storage.

OTHER HARD DISKSAn external hard disk is a separate free-standing hard disk that connects to your computer with a cable or wirelessly

A removable hard disk is a hard disk that you insert and remove from a drive

Internal and external hard disks are available in miniature sizes (miniature hard disks)

A disk controller sits between a hard disk and other parts in the computer like memory or CPU

- Consists of a special-purpose chip and electronic circuits.- Control the transfer of data to and from the disk through system bus.

Common disk controllers include:

DISK CONTROLLER

SATA EIDE

SCSI SAS

FLASH MEMORY STORAGE Flash memory chips are a type of solid

state media (like EEPROM) Non-volatile No moving parts (unlike hard disks) In the form of flash cards or solid state

drives (SSD) SSD is better than HD (and more

expensive) in the areas that:Shorter access timeHigher transfer ratesGenerate less heat and

consume less powerLast longer

FLASH MEMORY CARDS A memory card is a removable

flash memory device that you insert and remove from a slot in a computer, a mobile device or a card reader/writer.

from Wikipedia

from Wikipedia

from Wikipedia

from Wikipedia

FLASH MEMORY CARDS SD Cards (SD, SDHC, SDXC)

One of the most commonly used flash cards Current SDHC cards may have capacity of

128GB Different form factors: SD, Mini SD, Micro SD

Memory Stick (Duo, PRO Duo, PRO-HG) Originated from, and mainly used in Sony

Compact Flash (CFast) Much faster than SD, more expansive Mainly used in high-end digital camera

xD-Picture Card Originated from Olympus & Fujifilm Fading out

See this for a comparison of memory cardshttp://en.wikipedia.org/wiki/Comparison_of_memory_cards

USB FLASH DRIVE USB flash drives (or, thumb drives) are

plugged into a USB port on a computer. It’s very convenient:

Small, light-weight, removable, rewritable. But, handle with care!

Security is a big concern.

Have you heard about the news about

privacy data leakage through unattended USB thumb drives?

OPTICAL DISCS An optical disc consists of a flat, round,

portable disc made of metal, plastic, and lacquer that is written and read by laser.

Typically store software, data, digital photos, movies, music, etc. (mainly for archive)

Read only vs. rewritableDVD vs. DVD-R, DVD+R vs.

DVD-RW, DVD+RW, DVD-RAM

COMPACT DISCS (CD)A CD-ROM can be read from but not written to•Read from a CD-ROM drive or CD-ROM player•A capacity of 650MBA CD-R is a multisession optical disc on which users can write, but not erase•You may delete files, but the location can’t be used to store other data.

A CD-RW is an erasable multisession disc•Must have a CD-RW drive

DVD AND BLU-RAY DISCSA DVD-ROM is a high-capacity optical disc on which users can read but not write or erase•Requires a DVD-ROM drive, capacity : 4.7-17 GB•Single-sided, double-sided, single-layered, double-layered.

The most updated optical disc standard. A Blu-ray Disc-ROM (BD-ROM) has a storage capacity of 100 GB. Usually stores HD video.

DVD-RW, DVD+RW, and DVD+RAM are high-capacity rewritable DVD formats

MAGNETIC TAPES Tape is a magnetically coated ribbon of

plastic. It is capable of storing large amounts of data and information.

A tape drive reads and writes data and information on a tape sequentially.

MAGNETIC CARD & SMART CARD A magnetic strip

card contains a magnetic strip that stores information.

A smart card stores information on a thin microprocessor embedded in the card.

INPUT DEVICES

INPUT DEVICES Input (noun) is any data and

instructions entered into the memory of a computer.

An input device is any hardware component that allows users to enter data and instructions into a computer.

KEYBOARD A keyboard is an input device that

contains keys on which a user presses to enter input.

A standard input device in most of the computers.> 100 keysWired or wirelessSmall or virtual keyboards

on mobile devices.

USB port

Keyboard port

Wired Keyboards

Bluetooth

IrDA

Short range radio

Wireles

s Keyboards

POINTING DEVICES – MOUSE A pointing device is an input device

that allows a user to control a pointer on the screen

A pointer is a small symbol on the screen whose location and shape change as a user moves a pointing device

A mouse is a pointing device that fits under the palm of your hand comfortablyMost widely used pointing

device on desktop computers A mouse can be wired

or wireless

POINT DEVICES

Trackball•A trackball is a stationary pointing device with a ball on its top or side

Touchpad•A touchpad is a small, flat, rectangular pointing device that is sensitive to pressure and motion

Pointing Stick•A pointing stick is a pressure-sensitive pointing device shaped like a pencil eraser positioned between keys on a keyboard

TOUCH SCREENS & TOUCH-SENSITIVE PADS

Microsoft Surface

GAME CONTROLLERS Video games and

computer games use game controllers as the input devices that direct movements and actions of on-screen objects

Gamepads

Joysticks and Wheels

Light guns

Dance pads

Motion-sensing

controllers

DIGITAL CAMERAS Digital camera

A digital camera is a mobile device that allows users to take pictures and store them digitally.

ScannerFlatbedPen or handheldSheet-feddrum

Flatbed Pen or Handheld

Sheet-fed Drum

CAMERA QUALITIES Factors affecting image quality include:

Resolution

•Dimensions of the image in terms of pixels.•e.g., 640x480 (300k pixels), 3872x2592 (10M pixels)

No. of bits per pixel

•More bits more colors, more gray-shade levels.•e.g., 24-bit

Sensor (CCD) size

•Larger CCD more light collected per pixel more accurate color information•e.g., ½”, 1”, 4/3”, 35mm, etc.

WEB CAM A Web cam is a type of digital video

camera that enables a user to:Capture video and still imagesSend e-mail messages with video

attachmentsAdd live images to instant messagesBroadcast live images over the InternetMake video telephone calls

A video conference is a meeting between two or more geographically separated parties.

VOICE INPUT Voice input is the process of entering

input by speaking into a microphone Voice recognition is the computer’s

capability of distinguishing spoken words

Siri on iPhone 4S use your voice to send messages, schedule meetings, place phone calls, and more.

OCR Optical character recognition (OCR)

involves reading characters from ordinary documents.

A turnaround document is a document you return to the company that creates

BAR CODE READER A bar code reader, also called a bar

code scanner uses laser beams to read bar codes

RFID READER RFID (radio frequency identification)

uses radio signals to communicate with a tag placed in or attached to an object.

In HK, we have Octopus card (八達通 ) which uses RFID technology

An RFID reader reads information on the tag via radio waves

RFID can track:

Inventory

Location of soldiers

Employee wardrobes

Airline baggage

MAGNETIC STRIPE CARD READER

Reads the magnetic stripe on the back of cards such as:

Credit cards

Entertainment cards

Bank cards

Other similar cards

MICR A magnetic ink character recognition

(MICR) device reads text printed with magnetized ink.

An MICR reader converts MICR characters into a form the computer can process.

Bank industry uses MICR for check processing.

BIOMETRIC INPUT Biometric authenticates a person’s

identity by verifying a personal characteristic.

Fingerprint reader

Face recognition

system

Hand geometry system

Voice verification

system

Signature verification

system

Iris recognition

system

BIOMETRIC INPUT EXAMPLE

fingerprint

reader

hand geometry system

iris recognition system

OUTPUT DEVICES

OUTPUT DEVICES Output is data that have been

processed into useful forms.

WHAT IS OUTPUT? An output device is any type of

hardware component that conveys information to one or more people.

Display devices

Printers

Speakers, headphones, and earbuds

Data projectors

DISPLAY A display device visually

conveys text, graphics and video information.

A monitor is packaged as a separate peripheral.LCD monitorsLED monitorsWidescreen

DISPLAY The quality of an LCD monitor or LCD

screen depends primarily on:

Resolution

Response time

Brightness

Dot pitch

Contrast ratio

LED MONITORS It is a screen that uses Light Emitting Diodes to

portray different colored pixels. It has better contrast and is more efficient than the LCD Monitors which constantly has a flash lamp that is turned on and the Plasma and the old tube monitors.

The difference between LED and LCD is the back-light of the monitors. While the technology of the displays of LCD’s and LED’s is basically the same, the LCD monitor uses cold cathode fluorescent lamps as back-lights as compared to the LED monitors that emit diodes. CRT

Monitor

DIGITAL TV TV can also be used as

an output device.May require a converter

if you are connecting your computer to an analog computer.

Digital televisions offer a crisper, higher-quality display.

HDTV is the most advanced form of digital television.

PRINTERS A printer

produces text and graphics on a physical medium.Printed

information is called a hard copy, or printout.

Landscape or portrait orientation

NON-IMPACT PRINTERS A non-impact printer forms characters

and graphics on a piece of paper without actually striking the paper.

Ink-jet printers

Photo printers

Laser printers

Thermal printers

INK-JET PRINTERS An ink-jet printer forms characters

and graphics by spraying tiny drops of liquid ink onto a piece of paper.black-and-white, orcolors (CYMK)

Cyan, Yellow, Magenta

One key property of a printer is dpi (dots per inch).

PHOTO PRINTERS Produce color photo-

lab-quality pictures Mostly use ink-jet

technology PictBridge allows you

to print photos directly from a digital camera

Support printing from a memory card and preview photos on a built-in LCD screen

LASER PRINTERS High quality High speed

THERMAL PRINTERS A thermal printer generates images

by pushing electrically heated pins against the heat-sensitive paper.

PLOTTERSPlotters are used to produce high-quality drawings.Large-format printers create photo-realistic quality color prints on a larger scale.

IMPACT PRINTERS Impact printers from characters and

graphics on a piece of paper by striking a mechanism against an inked ribbon that physically contacts the paper.

Dot-matrix printer

Line printer

DOT-MATRIX PRINTERS A dot-matrix printer produces printed

images when tiny wire pins on a print head mechanism strike an inked ribbon.

Advantageous to print multiple copies at a time.

A line printer prints an entire line at a time.

LABEL PRINTERS A label printer is a

small printer that prints on adhesive-type material

A postage printer prints postage stamps

Postage also can be printed on other types of printers

AUDIO OUTPUT DEVICES An audio output device produces

music, speech or other sounds. E.g.,

Speakers, headphones, earbuds

Usage of speakers:Generate high-quality sounds

for playing games Interact with multimedia

presentationsListen to musicView movies, etc.

A 5.1 surround sound speaker

set.

AUDIO OUTPUT DEVICES Headphones are

speakers that cover our head or are placed outside your ears.

Earbuds (also called earphones) rest inside your ear canal.

AUDIO OUTPUT DEVICES Some speakers are specifically designed

to play audio from a portable media player.

E.g., wireless speakers with dock.

VOICE OUTPUT Voice output occurs when you hear a

person’s voice or when the computer talks to you through the speakers (and microphones).

Often works with voice input.

E.g., VoIP, Site readers

OTHER OUTPUT DEVICES

Data projectors

Interactive whiteboards

Force-feedback game

controllers

Tactile output

They are available for specific uses and applications.

PROJECTOR A data projector is a device that takes

the text & images displaying on a computer screen and projects them on a larger screen.E.g., digital light processing (DLP) projector

You’re now viewing a projector screen!

INTERACTIVE WHITEBOARD An interactive whiteboard is a touch-

sensitive device, resembling a dry-erase board, that displays the image on a connected computer screen

FORCE-FEEDBACK DEVICES Force-feedback

sends resistance to the device in response to actions of the user

Tactile output provides the user with a physical response from the device

OUTPUT FOR PHYSICALLY CHALLENGED USERS Many accessibility options exist for

users with various disabilities.

Braille printer

Magnifier

QUESTION DualShock and Wiimote, are they input

devices? Or output devices? Why?

ACTIVITY Imagine, one day, your boss asks you to copy

many data of a project to his client. As you know, the data files are about 2GB in

size. How will you help to pass the data to your

client? Why you choose that method or storage media?

SUMMARY Different secondary storage devices in

computer systems are introduced.Hard disk, SSD, Flash memory, USB thumb

drive, magnetic tape. Common output devices include

monitors, printers, speakers and projectors Various input devices can help us to

instruct or provide data to the computer.Keyboard, mouse, track ball, voice input,

web cam, scanner, OCR, biometric, etc.