CS 105 Spring 2006 Slide 1

Secondary Storage

• What is a cylinder? A track?

• What is secondary storage?

• What is flash memory?

See Unit B in your Concepts Book

CS 105 Spring 2006 Slide 2

What is Secondary (Auxiliary) Storage?

CD-ROMTape BackupHard disk Zip Drive

Floppy DisksDVD

RAMprimary storagemain memory,Needs power

ROM is built in,Can change only

slightly

CS 105 Spring 2006 Slide 3

Booting a computer uses ROM

• Bootstrapping: “to lift yourself up by your own bootstraps.”

• ROM is built-in memory, doesn’t change, needed when the power comes on.

• BIOS is a kind of Flash Memory, and can have some settings changed. Its name comes from basic input/output system (BIOS)

• Finally, software loaded into RAM

CS 105 Spring 2006 Slide 4

Units of Measure of Storage

• A binary digit; 0 or 1 = a Bit• 8 bits, or one character = a Byte (used for one letter)

• 1024 Bytes = 1 Kilobyte + or - 170 words

• 1024 Kilobytes = 1 Megabyte (1024*1024) + or - 175,000 words, about one floppy disk

• 1024 Megabytes = 1 Gigabyte • 1024 Gigabytes = 1 Terabyte + or - 179 million words

CS 105 Spring 2006 Slide 5

Size of storage

• A binary digit; 0 or 1 = a Bit

• 8 bits, or one character = a Byte(used for one letter)

1000001 is the letter A (65 in ASCII)

CS 105 Spring 2006 Slide 6

Thinking of storage

• The letter A is one byte

• 1 GB is like 1 billion letter A's.

• What if you could transfer one letter in each second?

• If there are 31,557,600 seconds in a year, and it would take about 31 years and seven months to transfer 1 GB of information that way!

CS 105 Spring 2006 Slide 7

More….

• A binary decision = 1 bit • A single text character = 1 byte • A typical text word = 10 bytes

• The complete works of Shakespeare = 5 megabytes

• A pickup truck filled with books = 1 gigabyte

• The contents of a DVD = 17 gigabytes

• A collection of the works of Beethoven = 20 gigabytes

CS 105 Spring 2006 Slide 8

Secondary Storage Devices

Provide permanent storage Slower to access than RAM

Direct access Magnetic Storage

Removable (Floppy disk/diskettes)Fixed (Hard disk)

____________Disk (CD)

Sequential accessMagnetic ___________

Used for cassettes, archives

CS 105 Spring 2006 Slide 9

Disk Organization

Tracks : Concentric circles where data is stored

Sectors : Pie-shaped wedges of tracks

CS 105 Spring 2006 Slide 10

Storing data on a hard drive

CS 105 Spring 2006 Slide 11

Disk Organization

Track 00

Track 39

Tracks and __________

Access Arm

CS 105 Spring 2006 Slide 12

Hard Disk Organization

•Cylinder : Combination of same-track locations on multiple-surface disks

CS 105 Spring 2006 Slide 13

Formatting a disk, losing your data

• When you format a disk, the operating system erases all bookkeeping information on the disk, tests the disk to make sure all sectors are reliable, marks bad (damaged) sectors, etc. You must format a disk before you can use it.

• Reformatting a disk does not erase the data on the disk, only the “directory” to find files.

CS 105 Spring 2006 Slide 14

CDs

Digital to Analog

CS 105 Spring 2006 Slide 15

Solid state storage and its advantages

• Flash memory in cameras and phones and home video game players, as secondary storage rather than RAM

• CompactFlash or SmartMedia cards are examples

CS 105 Spring 2006 Slide 16

Why not use Flash Memory everywhere?

• Flash memory is noiseless. • It allows faster access. • It is smaller in size. • It is lighter. • It has no moving parts.

BUT:• You can buy a 40-gigabyte (40,000-MB)

hard drive for less than $200, while a 192-MB CompactFlash costs more!

CS 105 Spring 2006 Slide 17

Since we are talking about Flash memory, what is a Smart Card?

• The term Smart Card is loosely used to describe any card with a capability to relate information

• Magnetic stripe • Memory, optical• Microprocessor cards

CS 105 Spring 2006 Slide 18

Memory card with a magnetic stripe – Memory is rewritable

• Your i-card has a cash stripe on the back of the card.• The dollar value placed on this stripe can be used to

make copies and for some campus purchases.• You add funds to the stored value stripe through

many of the Value Card Teller machines

CS 105 Spring 2006 Slide 19

Sim Cards

• A smart card fitted in every modern mobile phone which stores the phone's identity and settings.

• Phone numbers can be stored on the card

• Its primary function is to allow the networks to identify your phone to make calls.

• You can move the sim card from phone to phone, taking your info with you

• YOU CAN BACK UP YOUR SIM CARD, IN CASE YOUR CELLPHONE IS LOST!

CS 105 Spring 2006 Slide 20

Intelligent Smart Cards

• See definition: http://www.scsite.com/dc2000/ch6/display_terms.cfm?term=intelligent_smart_card

• Smart cards must have a central processing unit (CPU), random access memory (RAM), read only memory (ROM), and storage.

• The card not the terminal executes the series of commands and sends the results to the terminal

CS 105 Spring 2006 Slide 21

How are they used?

• Electronic purses (EP): smart cards which have stored value of electronic cash.

• No authentication is necessary

• Cards can be charged at special dispensers or by telephone and can be locked by a four digit code

• Can store value in up to five currencies

• Secure transactions—storing biometric data, etc.

CS 105 Spring 2006 Slide 22

Where do they get the power from?

• Smart cards rely on electricity from a smart card reader for the power they need to run.

• Wireless smart cards do not require electricity; instead, they have a built-in antenna that absorbs energy from nearby short-range electromagnetic fields.

• Thus, everyday objects can be made intelligent via "smart" devices.

• A toy, necklace, watch, shirt, etc. etc.

CS 105 Spring 2006 Slide 23

PC cards (USB Flash cards)

• PC Cards are credit card-size peripherals that add memory, mass storage, and other capabilities to computers—you plug them into the side of your laptop, usually.

Examples:• Hard Drives • Joystick Interface Cards • Memory Cards - Flash, SRAM, and many

others • Modem and Ethernet Combination Cards

CS 105 Spring 2006 Slide 24

Preset stations on your car’s radio

• If you turn the ignition off, a car radio still pulls a tiny amount of current from the battery. It saves its data in its RAM. (called also Flash RAM)

• That is why the car radio will lose its preset stations if your car battery dies or the wires are disconnected.

• Car radios ought to use Flash Memory—maybe one day they will.