1. COMPUTER MEMORY & DATA STORAGE

2. ROM ROM is short for Read Only Memory.
It is permanent, long-term memory which cannot be erased or changed in any way;
It is also known as “Non-Volatile Memory” because it doesn’t disappear after the computer is switched off.

3. ROM cont’d
ROM chips instruct the computer how to load the operating system from the hard drive into the computer’s memory.
Don’t confuse the hard drive with ROM – the hard drive is an internal backing store (storage device).

4. RAM RAM (Random Access Memory) is:-
Temporary, short-term working memory;
Only works when the computer is turned on;
It is also known as “Volatile Memory” because data disappears if the power is switched off.
Each time you start a program e.g. MS Word, it is loaded into RAM.
The amount of RAM influences processing power, speed and how many programs can run at the same time.
Many computers are now sold with 128 or 256 MB of RAM.

5. Measurement of Memory
Computer memory is measured in bytes.  A single byte is made up of a series of 1's and 0's, which are known individually as binary digits or “bits”. 
This is the way the computer communicates and stores information.  With each keystroke or character a byte of memory is used.
8 bits = 1 byte
1024 bytes = 1 kilobyte
1024 kilobytes = 1 megabyte
1024 megabytes = 1 gigabyte

6. Data Storage - 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. (1 Gb = 1024 Mb).

7. External Backing Store
USB Pens are a common external backing store, however only store up to 8GB of data.
When are they useful?
Excellent for transferring files of data from one machine to another and for backing up important files stored on your hard disk.

8. External Backing Store
CD-ROM (Compact Disk Read Only Memory) disks are optical disks that use the same technology as musical compact disks.
What can they be used for?
As CD-ROMs are much bigger than floppy disks, they can be used for multimedia applications such as encyclopedias and can store pictures, sounds and video clips.