What is Computer Storage

Refers to computer components and recording media that retain digital data.

• Primary storage

• Secondary storage

• Tertiary storage or tertiary memory,

• Off-line storage

Categories of Computer Storage:

COMPUTER STORAGE

Primary Storage Four Main Types of Primary Storage

Processor registers are located inside the processor.

Processor cache is an intermediate stage between ultra-fast registers and much slower main memory

RAM (Random Access Memory)- a volatile primary storage and the main memory of a computer that is directly connected to the cpu.

ROM (Read Only Memory) non-volatile primary storage containing a small startup program (BIOS) is used to bootstrap the computer,

Processor registers

Processor cache

RAM SDRAM stands for Synchronous Dynamic

Random Access Memory. DDR is short for "DDR SDRAM" and

stands for Double Data Rate.

Nowadays to avoid misunderstandings SDRAM is often specified as SDR SDRAM and SDR stands for Single Data Rate by analogy with DDR. Therefore, the main difference between SDR and DDR memory the doubled speed:

SDR SDRAM

RAM

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DDR1

• DDR1 RAM, also known as simply DDR SDRAM, has 184 pins that fit into the slot intended for it inside your computer on your motherboard.

RAM

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DDR2

•DDR2 SDRAM has 240 pins, and a notch at the bottom that is in a different location than the notch on DDR RAM.

RAM

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DDR3

DDR3 SDRAM (Double Data Rate Three Synchronous Dynamic Random Access Memory) is the third generation of DDR SDRAM

RAM

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Difference between SDR, DDR1, DDR2 and DDR3

RAMDesktop and Laptop DDR RAM

ROM Read-only memory (ROM): Type of primary storage where certain critical

instructions are safeguarded; the storage is nonvolatile and retains the

instructions when the power to the computer is turned off.

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Secondary StorageWhat is Secondary Storage? Holds data, instructions, and information for future use

Storage medium is physical material used for storage

Also called secondary storage

Secondary StorageWhat is capacity?

Kilobyte (KB) 1 thousand

Megabyte (MB) 1 million

Gigabyte (GB) 1 billion

Terabyte (TB) 1 trillion

Petabyte (PB) 1 quadrillion

Number of bytes (characters) a storage medium can hold

Exabyte (EB) 1 quintillion

Storage Medium(floppy disks, Zip disks,

hard disks, CDs)

Secondary StorageHow does volatility compare?

No

nvo

lati

le

Storage medium is nonvolatile—contents retained when power is off

Contents retained

Contents available to

user

Memory(most RAM)

(chips on motherboard)

Screen Display

ON OFF

Vo

lati

le Display disappears

Data andinstructions available to

user

Display appears

Data and instructions

erased

Memory is volatile—holds data and instructions temporarily

Writing

Process of transferring items from memory

to storage media

Writing

Process of transferring items from memory

to storage media

Secondary StorageWhat is a storage device?

Reading

Process of transferring items from storage media to memory

Reading

Process of transferring items from storage media to memory

Hardware that records and

retrieves items to and from

storage media

Functions as source of input

Creates output

Floppy Disk Small files to be transported

Secondary Storage

Primary Storage

Hard Disk

CDs and DVDs

Miniature Storage Media

Tape

Items waiting to be interpretedand executed by the processor

Operating system, applicationsoftware, user data and information

Software, backups, movies, music

Digital pictures or small files tobe transported

Backups

Memory (most RAM)

Stores …

Secondary StorageWhat is access time? Time it takes storage device to locate item on storage medium Time required to deliver item from memory to processor

fastertransfer

rates

slowertransfer

rates

Floppy DisksWhat is a floppy disk?

Portable, inexpensive storage medium (also called diskette)

Thin, circular, flexible film enclosedin 3.5” wide plastic shell

shutter

shell

liner

magneticcoating

flexible thin film

metal hub

Floppy DisksWhat is a floppy disk drive?

Floppy disk drive built intoa desktop computer

External floppy disk drive attaches toa computer with a cable

Also called secondary storage

One floppy drive, named drive A If two floppy drives, second

designated as drive B

Device that reads from andwrites to floppy disk

ExternalZip drive

Zip® DisksWhat is a Zip disk? Magnetic medium that stores 100 MB or 250 MB of

data

Zip disks require a Zip drivec—chigh capacity drive that reads from and writes on a Zip disk

Used to back up and to transfer files

Backup is duplicate of file, program, or disk in case original is lost

c

Zip disk

Hard DisksWhat is a hard disk?

hard disk installedin system unit

High-capacity storage Consists of several inflexible,

circular platters that store items electronically

Components enclosed in airtight, sealed case for protection

Hard DisksWhat are external hard disks and removable hard disks?

External hard disk—freestandinghard disk that connects to system unit

Removable hard disk—hard diskthat you insert and removefrom hard disk drive

Used to back up or transfer files

Push the same buttonto close the tray.

CDs and DVDsWhat are CDs and DVDs?

Most PCs include CD or DVD drive, most play audio CDs

Flat, round, portable metal discs with protective plastic coating

Can be read only or read/write Insert the disc,label side up.

Push the button toslide out the tray.

CDs and DVDsWhat is a CD-ROM? Compact disc read-

only memory Cannot erase or

modify contents Typically holds

650 MB to 1 GB Commonly used

to distributemultimedia and complexsoftware

CDs and DVDsWhat are CD-Rs and CD-RWs? Must have

CD recorderor CD-R drive

Cannot erasedisc’s contents

CD-R (compact disc-readable)—cdisc you can write on once

CD-RW (compact disc-rewritable)—ceerasable disc you can write on

multiple times

Must haveCD-RW softwareand CD-RW drive

CDs and DVDsWhat is a DVD-ROM (digital versatile disc-ROM or digital video disc-ROM)?

DVD

DVD drive

High capacity disc capable of storing 4.7 GB to 17 GB

Must have DVD-ROM drive or DVD player to read DVD-ROM

Stores databases, music, complex software, and movies

TapeWhat is tape? Magnetically coated plastic ribbon

capable of storing large amountsof data at low cost

Primarily used for backup

Miniature Mobile Storage MediaWhat is miniature mobile storage media? Storage for small mobile devices

Miniaturemobile storage

media

Miniature Mobile Storage MediaWhat are common types of miniature mobile storage media?

Smart Media Secure Digital

Microdrive ™ USBDrive™Memory Stick ®

CompactFlash

Miniature Mobile Storage MediaWhat is a card reader? Reads information stored on miniature mobile storage media Type of card determines type of card reader needed

Microfilm and MicroficheWhat are microfilm and microfiche?

Images recorded using computer output microfilm recorder

Store microscopic images of documents on roll or sheet of film

Microfilm — 100- to215-foot roll of film

Microfiche — small sheet of film, usually 4” 6”

Microfilm and MicroficheHow do life expectancies of various media compare?

Media Life Expectancies

Magnetic disks 3 to 5 years 20 to 30 years

CDs and DVDs discs 5 to 10 years 50 to 100 years

Microfilm 100 years 500 years

Media Type Guaranteed Life Potential LifeExpectancy Expectancy

Microfilm and microfiche have longest life of any storage media

Tertiary StorageA third level of storage. Typically it involves a robotic mechanism

which will mount (insert) and dismount removable mass storage media into a storage device according to the system's demands.

Offline Storage

is a computer data storage on a medium or a device that is not under the control of a processing unit.