StorageThe two types of storage:

Primary StorageSecondary Storage

Primary storage is also called Main Memory

Primary Storage

RAM ROM

Random Access Memory

Volatile- data lost if computer switched off

Short term storage of data

Read Only Memory Non-volatile- data

remains when computer is switched off

Long term / permanent storage of data

Difference between RAM and ROMRAM- is only filled after a computer has been turned on and given something to do.

ROM- holds data and instructions necessary for starting up the computer when it is switched on.

Next session….Secondary StorageNext Session

Secondary Storage

Is needed to store data and programs needed for later use.

Types of Secondary storage devices:

Magnetic Disks

Floppy disk Advantages:1)cheap to buy2)useful in

transferring 5.25” data

Disadvantages:1)very unreliable at

times 3.5’’

Magnetic Disks

Hard Disk Advantages:1)very fast to

access data since data can

be accessed directly

Magnetic TapeAdvantage:

Disadvantages:1)it is small

1)accessing data 2)It is cheap is very

slow3)It can store lots of data

Optical Disk

Compact Discs (CD) and Digital Video Discs (DVD)

Advantages:1)Can store lots of data (more than

floppy)

Flash Memory

Flash memory is a type of constantly powered nonvolatile memory that can be erased and reprogrammed in units of memory called blocks

Types:USB Flash drive / pen driveUSB stands for Universal Serial Bus

Memory CardA memory card or flash card is an

electronic flash memory data storage device used for storing digital

information

What is SD?Secure Digital (SD) is a nonvolatile 

memory card used extensively in portable devices, such as mobile phones, digital cameras, GPS navigation devices, handheld consoles, and tablet computers.

Secondary storage is also known as

Backing Store or Auxiliary Storage

Things to know:It is always slower to access data from backing storage than from main memory.

Data stored in backing storage is permanent so it is NOT lost when the computer is turned off.

Data stored in main memory is lost when the computer is turned off.

Next classWhat are the other types of Rom Write notes on the types of ROM

Class ActivityLook at the table in your text that

lists the storage devices (pages 38 & 39), their storage capacity and advantages and disadvantages.

Copy parts of the table into your notebook

QuestionsWhat is the difference between

CD-R and CD-RW?What is the storage capacity for

hard disks measured in?What is the storage capacity for

modern flash drives measured in?List the types of magnetic disks.

Components of a hard diskDraw and well labeled diagram for

a hard disk showing: sectors, tracks, cylinders, read-write heads, etc

VideoHow a hard drive works

Complete the following chart

Storage

Primary

RAM ?

?

Magnetic tape ?

Hard Disk ?

Optical Disk

? ?

?

Memory Card ?

Past Paper QuestionsAttempt ALLMay 2013 Q3Jan 2009 Q2Jan 2014 Q3Jan 2013 Q3

Access Methods

This term is used to refer to the mechanics of locating specific data at a particular place on a storage medium.

There are 2 types of access methods:

Direct AccessSequential Access

Direct AccessThis means that you can go

directly to a specific piece of data without having to access any other data either before or after the data you want

Sequential AccessMeans that data is retrieved

(accessed) in the order in which it was stored