Unit 3—Part A
Computer 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”
CDs
• A CD-ROM is a non-changeable cd, like the
ones people used to buy music on.
• A CD-R is a recordable cd. You can burn
information to it, but can’t delete files from it.
• CD-RW is the same as a CDR, but you can
delete information from this disk.
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