The two types of storage: Primary Storage Secondary Storage

Primary storage is also called Main Memory

Primary Storage Random Access Memory 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 Primary Storage

Difference between RAM and ROM RAM- 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 Storage

Is needed to store data and programs needed for later use. 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 buy 2)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 Tape Advantage: Disadvantages: 1)it is small 1)accessing data 2)It is cheap is very slow 3)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 drive USB stands for Universal Serial Bus

Memory Card A 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 class What are the other types of Rom Write notes on the types of ROM

Class Activity Look 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

Questions What 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 disk Draw and well labeled diagram for a hard disk showing: sectors, tracks, cylinders, read-write heads, etc

Video How a hard drive works

Complete the following chart Storage Primary RAM ? Magnetic tape Hard Disk Optical Disk Memory Card

Attempt ALL May 2013 Q3 Jan 2009 Q2 Jan 2014 Q3 Jan 2013 Q3 Past Paper Questions Attempt ALL May 2013 Q3 Jan 2009 Q2 Jan 2014 Q3 Jan 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 Access Sequential Access

Direct Access This 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 Access Means that data is retrieved (accessed) in the order in which it was stored