Module 5

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Module 5
Hardware
What Computers Do
Process Information
Produce Output
Receive Input
Store Information
4 Primary Components of a Computer
Secondary
Primary
- memory
- RAM
Storage
Devices
- tapes
Input
Devices
Processing
- keyboard
-CPU
- mouse
-Control Unit
- scanner
-Arithmetic &
Logic Unit
- touchpad
- removable disks
- CDs
- ROM
- digital camera
- hard disks
Output
Devices
- monitor
- printer
- speakers
Processing - CPU




“Central Processing Unit”
http://www.howstuffworks.com/microprocessor1.htm
 evolution of processors
the “brains” of the computer, where
calculations take place
two parts:
 ALU - Arithmetic Logic Unit
• electronic circuitry that does all
arithmetic and logic operations
 Control Unit
• circuitry that directs all other parts
of the computer
Input Devices

accept input from the outside
world.

most common is the keyboard,
followed by the mouse

sends signals to the computer,
telling it what you’ve “told” it
Output Devices

sends output to the outside world

converts and displays the
computer’s internal bit patterns to
a format that humans can
understand

Main output devices are


monitors for immediate visual output
printers for permanent paper output
Screen Output
 A monitor
or video display terminal
(VDT) displays characters, graphics,
photographic images, animation and
video.


Video adapter —connects the monitor to
the computer
VRAM or video memory—a special portion
of RAM to hold video images (the more
video memory, the more detail of a picture
displayed)
Screen Talk
 Monitor
size - measured as a diagonal
line across the screen.
 Pixels
(or picture element) - tiny dots that
compose a picture
 Resolution
- the number of pixels
displayed on the screen (the higher the
resolution, the closer together the dots)
Image Quality

Image quality is affected
by resolution and color
depth (or bit depth)
 Color depth refers to the
number of different colors
a monitor displays at the
same time
Examples of Color Depth
1-bit depth
8-bit depth
4-bit depth
16-bit depth
Paper Output

Printers produce
paper output or hard
copy

2 kinds of printers:
 Impact printers
 Non-impact printers
Impact Printers

Line printer



Used by mainframes to
produce massive printouts
Limited to printing
characters
Dot matrix printer



Images created by a
matrix of tiny dots
Low print quality
Low cost
Non-impact Printers
Laser Printer



A laser beam reflected off
a rotating drum to create
patterns of electrical
charges
Faster and more
expensive
than dot matrix printer
High-resolution output
More on Non-impact Printers
Ink-jet Printer



Sprays ink onto paper
to produce printed text
and graphic images
Prints fewer
pages/minute than laser
printer
High-quality color
costing less than laser
printer
Storage devices
Storage/Memory Devices
 Divided


into two groups:
Primary storage
• usually a temporary storage for the data and
programs currently in operation or currently
being accessed.
• it’s fastest and most expensive
Secondary storage
• long-term storage locations
• cheap but slower than primary memory
• some are portable/removable
• larger capacity than primary memory
Primary Storage - RAM

RAM: Random Access Memory
 very fast - access times < 1 billionth of a second – in
nanoseconds
 volatile storage - once the computer is turned off,
everything is lost
 this is where data and programs currently being used
reside

a document that has not yet been “saved” is in RAM and will
be lost if the computer freezes or the power goes off
Primary Storage - ROM

ROM = Read Only Memory
 permanent memory (doesn’t disappear if the
computer is turned off)
 normally holds the data/programs needed to start
(“boot up”) the computer
 typically, cannot be altered except by physically
changing the chip
RAM
ROM
Secondary Storage
 Secondary
storage devices are computer
peripherals capable of performing both
input and output functions
 Information is stored semi-permanently on
tape and disk drives
 Examples of storage devices



Magnetic tapes and disks
Zip, Jaz and SuperDisks
Optical disks
Secondary storage - Magnetic Tape
 Magnetic
tapes

Sequential access
Can store large amounts of information
in a small space at a relatively low cost

Limitation: sequential access

Used mainly for backup purposes

Magnetic Media

Magnetic drives




Random access
Floppy disks for inexpensive, portable
storage
Hard disks are typically non-removable,
rigid disks that spin continuously and
rapidly thus providing much faster access
than a floppy disk.
Removable media (Zip & Jaz disks)
provide high-capacity portable storage.
Hard Disk

magnetic storage
 data is saved until something is written over it (or
it gets damaged somehow)
 data saved on “platters” and read with a “head”
 platters spin at 3600-7200RPM


head can move to center and back to edge about 50
times per second
platters divided into “tracks” and “sectors” to make it
easier to retrieve data.
Optical Media
Optical disk drive uses laser beams to read
and write bits of information on the disk
surface.


Not as fast as magnetic hard
disks
Massive storage capacity and
reliability
Types of Optical Media

CD-ROM drives are optical drives that read
CD-ROMs.
 CD-R are WORM media (write-once, read
many). Hold about 700megabytes of info
 CD-RW can read CD-ROMs and write (onto
CD-R), erase and rewrite data onto CD-RW
disks.
 DVD (digital video disks) store & distribute all
kinds of data. They hold between 3.8 and 17
gigabytes of information.
Solid-state Storage Devices
Flash memory is an erasable memory chip.

Compact alternative

No moving parts


Designed for specific applications such as
storing pictures in digital cameras
Likely to eventually replace disk and tape
storage
Processing
The CPU
The microprocessor that makes up your personal
computer’s central processing unit, or CPU, is the
ultimate computer brain, messenger, ringmaster and
boss. All the other components—RAM, disk drives,
the monitor— exist only to bridge the gap between
you and the processor.
Ron White, in How Computers Work
The CPU
 The



CPU:
interprets and executes
instructions
performs arithmetic and
logical data manipulations
communicates with the
other parts
of the computer system.
The CPU

The CPU is a complex
collection of electronic
circuits.
 When all of those circuits
are built into a single silicon
chip, the chip is referred to
as a microprocessor.
 The circuit board that
contains a computer’s CPU
is called the motherboard
or system board.
motherboard
CPU
CPU Speed
 A computer’s
speed is determined in
part by the speed of its internal clock


The clock is a timing device that
produces electrical pulses to
synchronize the computer’s operations.
A computer’s clock speed is measured
in units called megahertz (MHz), for
millions of clock cycles per second
CPU Speed

Parallel processing
places multiple
processors in a
computer.

Most supercomputers
have multiple processors
that divide jobs into
pieces and work in
parallel on the pieces.
Ports and Slots
Tying things together
Ports and Slots
 The
system or motherboard includes several
standard ports:



Serial Port for attaching devices that
send/receive messages one bit at a time
(modems)
Parallel Port for attaching devices that
send/receive bits in groups (printers)
Keyboard/Mouse Port for attaching a keyboard
and a mouse
More on Ports and Slots
 Other
ports are typically included on
expansion boards rather than the system
board:



Video Port used to plug in a color monitor into
the video board
Microphone, speaker, headphone, MIDI
ports used to attach sound equipment
SCSI port allows several peripherals to be
strung together and attached to a single port
Expansion Made Easy
With the open architecture of the PC and the
introduction of new interfaces, you can now
hot swap devices.

USB (Universal Serial Bus) transmits a
hundred times faster than a PC serial port

Firewire (IEEE 1394) can move data between
devices at 400 or more megabits per second

high speed makes it ideal for data-intensive work
like digital video
Bits and Bytes
Information
Information comes in many forms
2
Text
Pictures
1
3
Numbers
Sounds
Computers store information in digital
form
Bit Basics
 A bit


On/off

(binary digit)
is the smallest unit of
information
can have two values: 1 or 0
can represent numbers,
codes, or instructions
Bits as Numbers
 Each
switch can be used to store a tiny
amount of information, such as:


An answer to a yes/no question
A signal to turn on a light
 Larger
chunks of information are stored by
grouping bits as units

8 bits (byte) = 256 different messages
Bits As Codes
ASCII – American Standard Code
for Information Interchange
Most widely used code, represents
each character as a unique 8-bit code.
Bits as Instruction
 The
computer stores instructions as
collections of bits. For instance,
01101010 might instruct the computer to
add two numbers.
 Other
bit instructions might include where
to find numbers stored in memory or
where to store them.
Bits, Bytes, and Buzzwords
Terms used to describe file size or memory size:





Byte
Kilobyte (KB)
Megabytes (MB)
Gigabytes (GB)
Terabytes (TB)
= 8 bits
≈ 1 Thousand Bytes
≈ 1 Million Bytes
≈ 1 Billion Bytes
≈ 1 Trillion Bytes
The logic machine

How do we build a computer that doesn’t need to be
rewired each time we want to perform a different task?

Connect the components in such a way that the
program itself controls the “rewiring” by signaling the
hardware to switch the components on and off in the
proper sequence
Logic Gates

Using switches, we can reproduce the logical
operators



AND
OR
NOT

0 = false = off

1 = true = on
AND
P
Q
PQ
0
0
0
0
1
0
1
0
0
1
1
1
AND is
written
like a
multiply
OR
P
Q
P+Q
0
0
0
0
1
1
1
0
1
1
1
1
OR is
written
like an
addition
NOT
P
P’
0
1
1
0
NOT is
written
with an ’
after the
letter
Simple Truth Table
P
Q
0
0
PQ + P’Q’
(result)
1
0
1
0
1
0
0
1
1
1
“if both P and Q
are the same,
then the result is
true”
Example:
check to see if P and Q are equal

Step 1: build Truth Table

The truth table for “P and Q are equal” looks like:
P
Q
Result
0
0
1
0
1
0
1
0
0
1
1
1
P = 0, Q = 0
they are equal
so result is
true (1)
P = 1, Q = 1
they are equal,
so result is true
(1)
Step 2:

Build an AND statement for each line where Result = 1
the ’ means
NOT… so P’
means that P is
off/0
P
Q
Result
0
0
1
P’ AND Q’ = P’Q’
1
1
1
P AND Q = PQ
Step 3:

Join each line with OR-statements
P’Q’ OR PQ
result = P’Q’ + PQ
Example 2:
Step 1: Build Truth Table … already done for us
P
Q
S
0
0
1
0
1
0
1
0
1
1
1
1
Step 2: Build equation terms using ANDs
P’Q’
PQ’
PQ
P
Q
S
0
0
1
0
1
0
1
0
1
1
1
1
P’Q’
PQ’
PQ
Step 3: Build equation by joining terms from step
2 with ORs
S = P’Q’ + PQ’ + PQ
Drawing circuits
Gates
Two
inputs
 AND
=
*
=
Two
inputs
 OR
=
+
=
’
One
output
=
One
input
 NOT
One
output
=
One
output
Gates to switches

Logical gates can be converted to physical
switches that operate exactly as expected

We can combine gates to act like our statements
from the truth tables since we have a gate for
each of AND, OR, NOT
Building Circuits
 We
build the circuit in the exact same
order as we build the equation




figure out the inputs
do all the NOTs
next all the ANDS
lastly all the ORs
Example
Result = PQ + P’Q’
Step A: Inputs
P
Q
One input (light
switch) for
each letter in
the equation
Result = PQ + P’Q’
Step B: NOTs
P
P
Q
Q
P’
Q’
Result = PQ + P’Q’
Remember
AND is the
same as a
multiply
Step C: ANDs
P
P
PQ
Q
P’
Q
P’Q’
Q’
Result = PQ + P’Q’
Remember
OR is the
same as
addition
Step D: ORs
P
Q
PQ
PQ + P’Q’
P’Q’
The light will light
up when the
inputs are both
the same, as
described in the
truth table
Example
3 inputs, light-up if exactly 2 inputs are true
Step 1: Build Truth Table
X
0
0
Y
0
0
Z
0
1
Result
0
0
0
0
1
1
1
1
0
0
0
1
0
1
0
1
0
1
1
1
1
1
0
1
1
0
Step 2: build terms with ANDs (where result is true)
X
0
Y
0
Z
0
Result
0
0
0
0
1
0
1
1
0
1
0
1
0
0
0
1
0
1
1
1
0
1
1
1
0
1
1
1
0
X’YZ
XY’Z
XYZ’
Step 3: Build equation by joining terms with ORs
result = X’YZ + XY’Z + XYZ’
Step 4: Build circuit
result = X’YZ + XY’Z + XYZ’
Step A: Inputs
X
Y
Z
result = X’YZ + XY’Z + XYZ’
Step B: NOTs
X
X’
Y
Y’
Z
Z’
result = X’YZ + XY’Z + XYZ’
Step C: ANDs
X
X’
X’Y
Y
X’YZ
Z
Y
Y’
XY’
X
XY’Z
Z
Z
Z’
Y
XY
X
XYZ’
result = X’YZ + XY’Z + XYZ’
X
X’YZ
Y
XY’Z
Z
XYZ’
result = X’YZ + XY’Z + XYZ’
X
X’YZ
X’YZ + XY’Z
Y
XY’Z
X’YZ + XY’Z+ XYZ’
Z
XYZ’
Using Loggo to combine gates

Go to the class homepage and look for the
Loggo applet in the Miscellaneous section
 Try implementing different equations to see if
they match the truth tables
Corresponding Readings
 Chapter
2
 Chapter 3
To Know – Module 5
 Vocabulary/definitions
 Truth



tables / circuits
From a description, write truth table
From truth table, write equation
From equation, build circuit
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