Computer memory

1. TEE COURSE GRADE 10
MODULE 7 - PC HARDWARE
Memory and Storage Devices

2. LEARNING OBJECTIVES
At the end of this lesson, students will be able to :
1. Meet the expectations of the Course Curriculum coded as:
TFV.01E, TF2.01E, TF2.02E, TF2.03E, TF2.04E, IC1.02E,
SPV.01E;
2. Explain the function and interaction of the primary (RAM, ROM)
and secondary storage devices (magnetic and optical);
3. Describe secondary storage devices: FDD, HD, CD-ROM, DVD;
4. Use precise terminology in relation to all storage devices;
5. Explain how data is stored on the surface of magnetic and
optical disks;
6. Uninstall and re-install main and secondary storage devices:
RAM, FDD, HD, CD-ROM;
7. Use safe practices in the handling of computer hardware and
electronic components.

3. Computer System Components
Central Processing Unit
Output
Devices
Cache
Memory
Primary
Storage
Secondary
Storage
Devices
Control
Unit
ALU
Special
Purpose
Processors
Output
Devices
Input
Devices
Short Review
Communication Devices

5. Three levels of memory hierarchy
Principle: the closer the memory is to the CPU, the faster it is.

6. Memory addresses
• Memory is a collection of
cells, each with a unique
physical/memory address
• Each cell can hold one
byte or 8 bits
101 102 103
201
301
202 203
302 303
With one by we can represent
one character in ASCII Code
Example: “A” is 65 in ASCII
code and 01000001 in binary
representation

7. Application/Thinking
How many bytes are in the phrase “You are
great!” .
a) 11
b) 13
c) 14
d) 1
So, this sentence will occupy __?__ cells in
memory

8. Storage Capacity
Unit
------------
kilobyte
megabyte
gigabyte
terabyte
petabyte
exabyte
Exact Number of bytes
------------------------
210 bytes
220 bytes
230 bytes
240 bytes
250 bytes
260 bytes
Approximation
------------
103 bytes
106 bytes
109 bytes
1012 bytes
1015 bytes
1018 bytes

9. Application/Thinking
How many megabytes (MB = 2 to the power
of 20 bytes) are in a terabyte (1TB = 2 to
the power of 40 bytes):
a) 2 to the power of 10
b) 2 to the power of 20
c) 2 to the power of 40
d) 2 to the power of 80

10. PRIMARY MEMORY: RAM AND ROM
•RAM (Random Access Memory) is volatile (temporary).
Programs and data can be written to and erased from RAM
as needed. This means that RAM does not retain its bit
configuration when the power is turned off, but ROM does
•ROM ( Read Only Memory) is nonvolatile (permanent). The
contents in locations in ROM cannot be changed
•It holds instructions that run the computer when it is
first turned on (BIOS)
•The CPU accesses each location in memory by using a
unique number, called a memory address.

11. Memory types- RAM
• RAM: random access memory
– SRAM: static RAM
• No need to be refreshed
– DRAM: dynamic RAM
• Need to be refreshed periodically
• Main memory
– SDRAM (Synchronous DRAM)
– EDRAM (Enhanced DRAM)
– EDO (Extended Data Out)
– FLASH RAM
– Ferroelectric RAM

12. Memory types– ROM
• ROM: read-only memory (Pre-programmed)
– PROM: programmable ROM
• Only written once
– EPROM: erasable PROM
• Use ultraviolet light to erase data
– EEPROM: electronically EPROM
• Can be erased using electronic impulses (higher
voltages)

13. Secondary Storage Devices
• Storage devices hold data, even when the
computer is turned off.
• The physical material that actually holds data is
called a storage medium. The surface of a floppy
disk is a storage medium.
• The hardware that writes data to or reads data
from a storage medium is called a storage
device. A floppy disk drive is a storage device.
• The two primary storage technologies are
magnetic and optical.

14. Magnetic Storage Devices
• Diskettes (floppy disks) (FDD)
• Hard disks (HD)
• High-capacity floppy disks (ZIP Disk)
• USB flash drive
• Magnetic tape

15. Optical Storage Devices
• Compact Disk Read-Only Memory (CD-ROM)
• Digital Video Disk Read-Only Memory
(DVD-ROM)
• CD-Recordable (CD-R)
• CD-Rewritable (CD-RW)
• PhotoCD

16. CLASSIFICATION- BIG PICTURE
Memory Types &
Storage Devices
Primary
Secondary
Volatile
Registers
Cache (I, II, III)
RAM
SRAM
DRAM
SDRAM
EDRAM
EDO
FLASH RAM
Non-volatile
ROM
PROM
EPROM
EEPROM
Magnetic memory
Tape
HD, Zip Disk
FDD
Optical
Memory
CD-ROM, CD-R, CD-RW
DVD-ROM, DVD-R
DVD- RW
(Semiconductor –
chip). Main Memory
(Devices)
2ns
5ms

17. Magnetic Storage Devices
- How Magnetic Storage Works
• A magnetic disk's medium contains iron
particles, which can be polarized—given a
magnetic charge—in one of two directions
(north or south).
• Each particle's direction represents a 1 (on) or 0
(off), representing each bit of data that the CPU
can recognize.
• A disk drive uses read/write heads containing
electromagnets to create magnetic charges on
the medium.

18. As the medium
rotates, the head
writes the data.

19. Magnetic Storage Devices - Diskettes
• Diskette drives, also known as floppy disk drives,
read and write to diskettes (called floppy disks or
floppies).
• In disks the areas to save data are organized as a
set of concentric circles called Tracks. Floppy disks
have 80 tracks. The disks are further divided into
pie-slice Sectors.
• 300 rpm
• Diskettes size: 3.5-inch.

20. Formatted Disk

21. 3.5 inch
floppy
and drive

22. Hard Disk Drive
• Purpose:
– Long-term, nonvolatile storage
– Large, inexpensive, slow level in the storage
hierarchy
• Disk composition
– A magnetic disk consist of a collection of platters
(1to 20 per disk) that rotate on a spindle.
– Disk surface divided into tracks (1000 to 4800 per
platter).
– Tracks are divided into sectors (64 per track), which
are the smallest unit that can be read or written.
• Up to 10,000 rpm

23. Magnetic Disks
• A read/write head travels across a spinning magnetic
disk, retrieving or recording data
The organization
of a magnetic disk

24. Optical Storage Devices –
How Optical Storage Works
• An optical disk is a high-capacity storage
medium. An optical drive uses reflected light to
read data.
• To store data, the disk's metal surface is
covered with tiny dents (pits) and flat spots
(lands), which cause light to be reflected
differently.
• When an optical drive shines light into a pit, the
light cannot be reflected back. This represents a
bit value of 0 (off). A land reflects light back to
its source, representing a bit value of 1 (on).

25. 1 0

26. Optical storage devices
• CD-ROM: compact disc ROM (Read Only Memory)
– Capacity: 650MB
• CD-R: compact disc recordable
• CD-RW: compact disc rewritable
• DVD: digital versatile disc
– Capacity: 4.7GB – 17GB
• DVD-R
• DVD-RW (2 versions: + (plus) and
– (dash)

27. DVD (Digital Versatile Disk)
– Allows up to 17 gigabytes of storage (from 4.7
GB to 17 GB).
– Compatible with older CD-ROM technology.
– The four versions of the DVD:

28. lesson Review
• List four types of magnetic and four types of optical
storage devices.
• Identify two common uses for floppy disks.
• Explain how data is stored on the surface of magnetic
and optical disks.
• List three variations on optical disk technology.

29. EVALUATION
1. Cache memory has the fastest speed: T F
2. A TB has 1024 MB? T F
3. EPROM is a volatile memory? T F
4. SRAM needs to be refreshed? T F
5. EEPROM use ultraviolet light to erase data?T F
6. A land reflects light back to its source,
representing a bit value of 1 (on). T F
7. A pit, does not reflect the light back and this
represents a bit value of 0 (off). T F

30. EVALUATION – SHORT TEST cont’ed
8. Define the following acronyms:
• SRAM ______________________________
• DRAM ______________________________
• SDRAM ______________________________
• EDRAM ______________________________
• PROM ______________________________
• EPROM ______________________________
• EEPROM ______________________________
• CD-ROM ______________________________
• HDD ______________________________
• FDD ______________________________
• DVD RW ______________________________
• CD-RW ______________________________