Unit 3—Part AComputer Memory

Computer Technology(S1 Obj 2-3)

Memory

• Memory: The area in the computer that temporarily holds data waiting to be processed

RAM• RAM stands for Random Access Memory• It is the memory that holds your data as you

manipulate (process) it. • The data stays in RAM until you save it.• RAM is volatile which means ‘temporary memory.’ • No data can be stored in RAM when the power to the

computer is off. Data is lost if the computer looses power

RAM continued…• The more RAM you have, the more

multitasking you can do on your computer. • If you don't have enough RAM, you may

notice that your computer is sluggish when you have several programs open.

• Many people add extra RAM to their computers to improve performance.

ROM• ROM stands for Read Only Memory• ROM contains the instructions the computer uses

when it ‘boots up’• Because the data is ‘read only’, it can be read but

not changed by the user.• The data is not erased when the computer is

switched off—the data is stored permanently. This is called ‘non-volatile memory’

• Therefore, ROM is “permanent memory”

Binary Code• Binary code is the language that computers

use to communicate and process information. • It is a coding system using the 0 and 1 to

represent a letter, digit, or symbols in a computer or other electronic device.

BIT• Each 0 or 1 is called

a bit• A bit is the smallest

unit of information that a computer handles

• A single bit conveys little meaningful information

BYTE• A combination of eight bits is called a byte.• One byte (8 bits) represents a single letter,

symbol, or digit.

A 2 letter word = 2 bytes, 16 bits

Kilobyte• One kilobyte (KB) is equal to 1,024 bytes• Kilo is a prefix meaning thousand• Kilobyte = approximately one thousand bytes• Most of the user data stored in a computer,

such as simple e-mail messages or a text file, occupies storage space of a few kilobytes

Megabyte

• One megabyte (MB) is equal to 1,024 KB. • Mega = Million• Megabyte = Approximately one million bytes• The amount of information contained in 1 MB

is approximately equal to one complete textbook.

Gigabyte

• One gigabyte (GB) is equal to 1,024 MB

• Giga = Billion• Gigabyte = Approximately

one billion bytes• Some videos stored on a

computer can occupy more than 1 GB of space.

Trivia

• Remember when 3.5" floppy diskettes were all the rage?

• It takes 728,178 floppy disks to equal the storage capacity of a 1 GB hard drive.

• The storage capacity of hard drives today are measured in hundreds of Gigabytes up to a few Terabytes.

Terabyte

• One (TB) is equal to 1,024 GB• Tera = Trillion• Terabyte = Approximately one

trillion bytes• Let's assume we're storing

text from magazine pages. At an average 5,000 characters per page, 1TB of disk space could hold 220 million pages of text!

Petabyte• Petabyte (PB)= approximately one quadrillion

bytes• Google processes approximately 24 petabytes

of data each day. • AT&T transfers approximately 30 petabytes of

data through it’s networks each day.

In January 2012, Cray began construction of the Blue Waters Supercomputer, which will have a capacity of 500 petabytes making it the largest storage array ever when it is completed.

Exabyte• Exabyte (EB) = approximately one quintillion bytes• In the next decade, astronomers expect to be

processing 10 petabytes of data every hour from a telescope called the Square Kilometer Array (SKA).

• The telescope is expected to generate approximately one Exabyte every four days of operation.

• IBM is currently designing hardware to process this information