Computer memory ppt test

1. Computer Memory and Data
Storage

2. Lesson Objectives
Understand the relationship between
different units of measurement of
computer memory.
Use this knowledge to select the most
appropriate method of storage.
Understand the difference between
RAM and ROM and are able to define
them.

3. ROM
ROM stands for Read Only Memory:
It is permanent, long term memory, which
cannot be changed or erased is any way.
It is also known as non-volatile memory
because it is not lost when the computer is
turned off.
ROM Chips instruct the computer how to load
the operating system from the hard drive into
the computers memory.

4. RAM
RAM stands for Random Access Memory.
Temporary, short term working memory.
Only works when the computer is turned on.
It is also know as volatile memory because
data disappears once the computer is turned
off.
Each time you start a program it is loaded into
the RAM.
The amount of RAM influences the processing
power, speed and how many programs can
run at the same time.

5. Measurement of Memory
Computer memory is measured in bytes.
A single byte is made up of 1’s and 0’s.
These are known as binary bits.
1
Kilobyte
(kb)
= 1024
Bytes
1
Megabyte
(Mb)
= 1 048
576
Bytes
1
Gigabyte
(Gb)
= 1024 Mb

6. Data Storage

7. Data Storage
It is very important to have a device on
which to store data and programs when the
computer is turned off.
There are two main types of external
storage.
Magnetic Media
Optical Drives

8. Magnetic Media
This category includes:
Hard Drives
Floppy Disks
Tape Drives
 These are the most common, and cheapest
way to store data.

9. Internal Backing Store
Hard disks are the main internal backing store
usually found inside computers.
The main benefit of hard drives is that they
have a large storage capacity – 20 Gigabytes
or more (1Bg = 1024 Mb).

10. Floppy Disks
 Floppy Disks were common external storage
devices.
 They only store up to 1.44Mb of data.
 When are they useful?
 Transferring small files between computers.
 Backing up small files.
 Why do you think they are not so common
anymore?

11. Magnetic Tape
Large organisations who need to back up their
systems daily tend to use magnetic tapes to
store their data.
Works like a video tape. To find a specific
piece of data, you have to start at the
beginning of the tape and continue fast
forwarding until you get to the piece of data
that you need.
This makes it fairly slow to find and retrieve
data so it would not be much use to store data
that you needed to get hold of quickly.

12. Optical Drives
This category includes:
CD-ROM
CD-R
DVD

13. CD-ROM
 Stands for Compact Disk – Read Only
Memory
 They store up to 700 Mb of data and a
laser beam is used to read the data off the
disk.
 What can they be used for?
 Much bigger than a floppy disk.
 Can be used for multimedia applications
and to store sound, video and pictures.

14. DVD
Stands for Digital Versatile Disk
A DVD is similar to a CD.
A single sided DVD can store
about 4.7Gb of data. Double sided
DVDs can hold over 9Gb of data.
Different companies which make
DVD’s haven't agreed on a
standard format.

15. Flash Drives
Flash memory storage devices are
typically small, lightweight,
removable and rewritable.
They usually have a removable
cap which covers and protects the
part of the stick which is inserted
into a USB port.
Memory sticks are available from 1
Gb up to 8Gb.