Computer memory and storage

1. Lecture # 4
Memory Vs Storage

2. Memory and Storage
• Both terms are used to refer to internal
storage space on a computer. Memory, usually
referred to as Random Access Memory (RAM),
is the place where an application loads its data
during processing, while a hard disk drive is
usually the place where data is stored for long
or short term retention.

3. Memory
What is memory?
p. 193 Fig. 4-17 Next
 Electronic components that store
instructions, data, and results
 Consists of one or
more chips on
motherboard or
other circuit board
 Each byte stored
in unique location
called an address,
similar to seats
on a passenger train
Seat #2B4 Seat #2B3

4. Memory
How is memory measured?
p. 194 Fig. 4-18 Next
Term Abbreviation Approximate Size
Kilobyte KB or K 1 thousand bytes
Megabyte MB 1 million bytes
Gigabyte GB 1 billion bytes
Terabyte TB 1 trillion bytes
 By number of bytes available for storage

5. Memory
What is random access memory (RAM)?
Next
The more RAM a
computer has, the
faster it responds
Also called
main memory
or primary
storage
Most RAM is
volatile, it is lost
when computer’s
power is
turned off
Memory chips that can be
read from and written
to by processor

6. Types of RAM
• There are two different types of RAM: DRAM
(Dynamic Random Access Memory) and SRAM
(Static Random Access Memory).
• DRAM needs to be refreshed thousands of
times per second while
• SRAM does not need to be refreshed, which is
what makes it faster than DRAM. Both types
of RAM are volatile, meaning that they lose
their contents when the power is turned off.

7. Memory
What is flash memory?
p. 199 Fig. 4-24 Next
Step 1.
Purchase and download MP3 music tracks
from a Web site. With one end of a special
cable connected to the system unit, connect
the other end into the MP3 player.
Step 2.
Instruct the computer to copy the MP3 music track
to the flash memory chip in the MP3 player.
Step 3.
Plug the headphones into the MP3
player, push a button on the MP3
player, and listen to the music
through the headphones.
MP3 Player
Flash memory chip
Flash memory card
From computer
To headphones
 Nonvolatile memory that can be erased electronically and
reprogrammed
 Used with PDAs, digital cameras, digital cellular phones, music players,
digital voice recorders, printers, Internet receivers, and pagers

8. Storage
What is storage?
p. 348 Fig. 7-1 Next
 Holds data, instructions, and information for future use
 Storage medium is physical material used for storage
 Also called secondary storage

9. Floppy Disks
What is a floppy disk drive?
p. 352 Fig. 7-6 Next
Floppy disk drive built into
a desktop computer
External floppy disk drive attaches to
a computer with a cable
 Also called secondary storage
 One floppy drive, named drive A
 If two floppy drives, second
designated as drive B
 Device that reads from and
writes to floppy disk

10. Hard Disks
What is a hard disk?
p. 355 Fig. 7-12 Next
hard disk installed
in system unit
 High-capacity storage
 Consists of several inflexible,
circular platters that store items
electronically
 Components enclosed in airtight,
sealed case for protection

11. Hard Disks
What are external hard disks and removable hard disks?
p. 359 Fig. 7-18 Next
External hard disk—freestanding
hard disk that connects to system unit
Removable hard disk—hard disk
that you insert and remove
from hard disk drive
 Used to back up or transfer files

12. Push the same button
to close the tray.
CDs and DVDs
What are CDs and DVDs?
p. 361 Fig. 7-20 Next
 Most PCs include CD or DVD
drive, most play audio CDs
 Flat, round, portable metal
discs made of metal, plastic,
and polish.
 Can be read only or read/write
Insert the disc,
label side up.
Push the button to
slide out the tray.

13. CDs and DVDs
What is a CD-ROM?
p. 363 Fig. 7-24 Next
 Compact disc read-
only memory
 Cannot erase or
modify contents
 Typically holds
650 MB to 1 GB
 Commonly used
to distribute
multimedia and
complex
software

14. CDs and DVDs
What are CD-R and CD-RW?
p. 366 Next
Must have
CD recorder
or CD-R drive
Cannot erase
disc’s contents
CD-R (compact disc-readable)
—cdisc you can write on once
CD-RW (compact disc-rewritable)
—ceerasable disc you can write on
multiple times
Must have
CD-RW software
and CD-RW drive

15. CDs and DVDs
What is a DVD-ROM (digital versatile
disc-ROM or digital video disc-ROM)?
p. 368 Fig. 7-27 Next
DVD
DVD drive
 High capacity disc capable of storing 4.7
GB to 17 GB
 Must have DVD-ROM drive or DVD
player to read DVD-ROM
 Stores databases, music, complex software,
and movies

16. Tape
What is tape?
p. 370 Fig. 7-29 Next
 Magnetically coated plastic ribbon
capable of storing large amounts
of data at low cost
 Primarily used for backup

17. Miniature Mobile Storage Media
p. 373 Fig. 7-35 Next
What is a card reader?
 Reads information stored on miniature mobile storage media
 Type of card determines type of card reader needed