1. The two types of storage: Primary Storage Secondary Storage

2. Primary storage is also called Main Memory

4. 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

5. 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.

6. Next session….Secondary Storage

7. 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:

8. Magnetic Disks Floppy disk Advantages: 1)cheap to buy
2)useful in transferring
5.25” data
Disadvantages:
1)very unreliable at times
3.5’’

9. Magnetic Disks
Hard Disk Advantages: 1)very fast to access data since data can be accessed directly

10. 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

11. Optical Disk
Compact Discs (CD) and Digital Video Discs (DVD) Advantages: 1)Can store lots of data (more than floppy)

12. 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

13. 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.

14. Secondary storage is also known as Backing Store or Auxiliary Storage

15. 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.

16. Next class What are the other types of Rom
Write notes on the types of ROM

17. 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

18. 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.

19. Components of a hard disk
Draw and well labeled diagram for a hard disk showing: sectors, tracks, cylinders, read-write heads, etc

20. Video
How a hard drive works

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

22. 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

23. 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

24. 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

25. Sequential Access
Means that data is retrieved (accessed) in the order in which it was stored