Transcript Shelly Cashman Series Discovering Computers 2002

History
 1851
successful cabling between
England and France
 1956, first transatlantic telephone
cable
 1988, first transatlantic fiber optic
cable
1855
Cable Laying Ships
Cable-laying ships Agamemnon and Niagara in Atlantic storm.
From Harper's Weekly: Telegraph Supplement (September 4, 1858)
History
History
Cartoon
"New Siamese Twins"
The telegraph links England and
France
British political cartoon,
Punch magazine, 1851
Atlantic Cable
Portion of Atlantic cable, 1865-66 (retrieved from the Atlantic in 1939)
National Museum of American History
Cabling Ship
Flag State:
Norway
Class:
DNV Cable Layer
Cable Capacity:
6400 mt
Beam:
22 mtr
A-Frame SWL:
50 mt
Endurance:
100 Days
Year Built:
2000
LOA:
121 mtr
Maximum Speed:
16 knots
Draft:
7.3 mtr
Repeaters:
160
Duplex DP System
Helideck
Bollard Pull
150 mt
Berthing:
70 persons
Under Sea Installation
Planning
Under Sea Installation
Planning
•Environmental Assessment
Bringing the Cable
Ashore




1857: First Try
Cable snaps 30 miles off Irish coast. No one had ever laid cable in water
so deep before, so no one knew what problems to expect.
1858: Second Try, Momentary Success
Using improved machinery, two ships lay cable from mid-ocean to
Ireland and Newfoundland. North America and Europe are linked for
instant communication.
Unfortunately, the cable fails within a month.
1865: Third Try
Two-thirds of the way across the Atlantic, the cable breaks.
1866: Success!
Cable successfully connects Europe (Ireland) and North America
(Newfoundland).
Internet Infrastructure
Mercy
College
Internet
Server
It is a global collection of networks, both big and small.
These networks connect together in many different ways to form the single entity that we know as the Internet.
In fact, the very name comes from this idea of interconnected networks.
Large ISP, UUNET
Most large communications
companies have their own
dedicated backbones
connecting between
various regions.
In each region, the company
has a
Point of Presence (POP).
The POP is a place for local
users to access the
company's network,
often through a local phone
number or dedicated line
Large ISP, UUNET
What are Fiber Optics

Fiber optics (optical
fibers) are long, thin
strands of very pure
glass about the
diameter of a human
hair. They are
arranged in bundles
called optical cables
and used to transmit
light signals over
long distances.
It has following parts:
•core - thin glass center of the fiber where the light travels
•cladding - outer optical material surrounding the core that reflects the light back into the core
•buffer coating - plastic coating that protects the fiber from damage and moisture
How Does an Optical
Fiber Transmit Light?



Suppose you want to shine a flashlight beam down a long, straight
hallway.
Just point the beam straight down the hallway -- light travels in straight
lines, so it is no problem.
What if the hallway has a bend in it? You could place a mirror at the
bend to reflect the light beam around the corner. What if the hallway was
very winding with multiple bends? You might line the walls with mirrors
and angle the beam so that it bounces from side-to-side all along the
hallway. This is exactly what happens in an optical fiber.
How Does an Optical
Fiber Transmit Light?

The light in a fiber optic cable travels through the core (hallway) by
constantly bouncing from the cladding (mirror-lined walls), a principle
called total internal reflection. Because the cladding does not absorb any
light from the core, the light wave can travel great distances. However,
some of the light signal degrades within the fiber, mostly due to
impurities in the glass.
The System Unit
What is the system unit?
Box-like case
that houses
the electronic
components
of the
computer
used to
process data
 All computers
have a
system unit
 Sometimes
called the
chassis

The System Unit
What are common components inside the
system unit?




Processor
Memory module
Expansion cards
• Sound card
• Modem card
• Video card
• Network
interface
card
Ports and
Connectors
The System Unit
What is the motherboard?
Also called the system board
 Main circuit board in the
system unit
 Contains many
electronic
components

The System Unit
What electronic components are found
on the motherboard?
Chip
Small piece of semi-conducting material on
which one or more integrated circuits are
etched
Integrated Circuit (IC)
Microscopic pathway capable of carrying
electrical current
Transistor
Acts as an electronic switch, or gate,
that opens or closes the circuit
for electronic signals
Central Processing Unit
What is a personal computer processor?
The single processor chip found in personal
computers
 Sometimes called a microprocessor
 Processors identified by
• Manufacturer
• Model name or

model number
Pentium® 4
Celeron™
Athlon™
Duron™
Central Processing Unit
What is the central processing unit (CPU)?



Interprets and carries out the basic instructions that operate a
computer
Most devices communicate with the CPU in order to carry out a task
Also called the processor
Central Processing Unit
What are the components of the
central processing unit (CPU )?
CPU
Control Unit
Arithmetic/
Logic Unit
(ALU)
Central Processing Unit
What is the control unit?

A component of the CPU that
directs and coordinates most
of the operations in the
computer
CPU
The control unit repeats a
set of four basic operations:
 Fetch – obtain
a program
Arithmetic/
Control
Unit
instructionLogic
or dataUnit
item from
Control Unit
memory
(ALU)



Decode - translate the instruction
into commands
Execute - carry out the command
Store - write the result to memory
Central Processing Unit
What is the arithmetic/logic unit (ALU)?



Component of the CPU
Performs arithmetic, comparison, and logical
operations
Performs the execution part of the machine cycle
CPU
Control Unit
Next
p. 4.6
Arithmetic/
Logic Unit
(ALU)
Central Processing Unit
What is the arithmetic/logic unit (ALU)?
Comparison
(greater than, equal
to, or less than)
Arithmetic
p. 4.6
(addition, subtraction,
multiplication, and
division)
Logical
(AND, OR,
NOT)
Central Processing Unit
What is a machine cycle?
 Together
the four operations of the CPU comprise a
machine cycle
 Also called an instruction cycle
• Instruction time (i-time) - time it takes to fetch and decode
• Execution time (e-time) – time it takes to execute and store
e-time
i-time
Central Processing Unit
What is a machine cycle?
 Together
the four operations of the CPU comprise a
machine cycle
A student enters a
math problem into
Step
1: The control
the memory
of the
unit
fetches the
computer
Step
The control
math 2:
problem
from
unit
Stepdecodes
4:The
TheALU
the
memory
Step
3:
math
results
problem
ofthe
themath
and
executes
sends
math problem
it to the ALU
are
problem
stored in memory
The result in
memory displays
on the screen of
the monitor
Central Processing Unit
How is the speed of the CPU measured?

According to
how many
millions of
instructions per
second (MIPS) it
can process
Central Processing Unit
What is the system clock?
Synchronizes all
computer
operations
Faster
clock speed
means the CPU
can execute more
instructions each
second
Clock speed
(clock rate)
measured in
megahertz
(MHz) and
gigahertz
(GHz)
MHz - one
million ticks of
the system
clock
GHz – one
billion ticks of
the system
clock
Central Processing Unit
How do personal computer processors compare?
p. 4.9 Fig. 4-10
Data Representation
How do computers represent data?

Most computers are digital
• Computers are electronic devices
powered by electricity, which has only
two states, on or off
• Computers recognize only two
discrete states: on or off
on
off
Next
p. 4.13
1
1
0
1
0
1
0
1
0
0
Data Representation
What is the binary system?


A number system that has just two unique digits, 0 and 1
• A single digit is called a bit (binary digit)
• A bit is the smallest unit of data the computer can represent
• By itself a bit is not very informative
The two digits represent the two off and on states
Binary
Digit (bit)
Electronic
Charge
Electronic
State
Data Representation
What is a byte?


Eight bits are grouped together to form a byte
0s and 1s in each byte are used to represent
individual characters such as letters of the
alphabet, numbers, and punctuation
8-bit byte for the number 3
8-bit byte for the number 5
8-bit byte for the capital letter T
Data Representation
What are two popular coding systems to
represent data?



American Standard
Code for Information
Interchange (ASCII)
Extended Binary Coded
Decimal Interchange
Code (EBCDIC)
• Sufficient for English
and Western
European languages
Unicode often used for
other languages
Data Representation
How is a character sent from the keyboard to the
computer?
Step 1:
The user presses the letter T key
on the2:keyboard
Step
An electronic signal for the letter
T
is sent
Step
3: to the system unit
The signal for the letter T is
converted to its ASCII binary
code (01010100) and is stored in
memory
Step 4: for processing
After processing, the binary
code for the letter T is converted
to an image on the output device
Next
p. 4.15 Fig. 4-17
Technology Trailblazer
Gordon Moore




Co-founder of Intel
Witnessed a
consistent
geometric growth
in technology
Developed
principle called
Moore’s Law in
1965
Moore’s Law
• The number of transistors and resistors placed on
computer chips would double every year, with a
proportional increase in computing power and decrease
in cost. This principle held true until 1975, when he
changed the prediction to doubling every two years.
Memory
What is memory?
 Temporary
storage place for data, instructions, and
information
 Consists of one or more chips on the motherboard or
some other circuit board
operating system and other system software
that control the usage of the computer
equipment
 Three
basic
items stored
in memory
application programs that carry out
a specific task
data being processed by
application programs
Memory
How are bytes
stored?





Bytes are the basic
storage unit in memory
Each byte is stored at a
specific location in
memory called an address
Each address has a
unique identifying number,
like the seats on an
airplane
Each address can hold
only a single byte
Each address can be full
or empty
seat C22
seat B22
seat A22
Memory
How is memory measured?

Size of memory is measured by the number of
bytes available
• Kilobyte - 1,024 bytes
• Megabyte - one million bytes
Memory
What are the two types of memory in the
system unit?
volatile
Volatile memory
Memory
Loses
itscontents
contents
when
Loses its
when
the
the computer's
computer's
power ispower
turnedis
off
turned off
nonvolatile
memory
Does not lose its
contents when the
computer’s power is
turned off
Memory
What is random access memory (RAM)?
Memory chips that can be read from and
written to by the processor and other devices
When the computer starts, operating system
files are loaded from a hard disk into RAM
As additional programs and data are requested,
they also load from storage into RAM
Most RAM is volatile
Memory
How are applications transferred in and out of RAM?
Step 1: When your
computer is
Step 2: When you
running, certain
start a word
operating
system
Step
3: When
you
processing
program
files
are in RAM
RAM.may
quit
suchWord,
Step
4:
5:
as When
Word, you
the
Shown
here
is
the
be
used
to
store
program
start
quit
Excel,
a spreadsheet
loads
RAM
into
may
operating
system’s
another
program
RAM
program
be
used
from
to
such
astore
hard
as or
user
interface.
data.
The
program
disk. As
Excel,
another
the
program
you
program
create
or
is
removed
from
the
a document,
loads
data.
Excel
into RAM
is
it isfrom
in
screen
and
the
RAM
a
removed
hardand
disk.
from
displays
Asyour
you
operating
system’s
on youraand
create
screen
screen.
spreadsheet,
the
user
it is ininterface
operating
RAM
system’s
and
redisplays.
displays
user
interface
on your
screen.
redisplays.
Storage
(hard
disk)
RAM
Memory
What is a memory module?

RAM chips
usually reside on
a small circuit
board which
inserts into
motherboard
memory chip
dual inline
memory module
(DIMM)
Memory
How much RAM is needed?

The more RAM, the
more programs and
files a computer can
work on at once

Software package
usually indicates
how much RAM is
required
Next
p. 4.18 Fig. 4-22
Memory
How much RAM is needed?

Necessary RAM depends on what type of
applications you intend to run on your computer
Memory
What is memory cache?

Also called cache store or
RAM cache

Helps speed the
processes of the
computer by storing
frequently used
instructions and data

When the processor needs
an instruction or data, it
first searches cache. If it
cannot locate the item in
cache, then it searches
Memory
What is memory access
time?



Speed at which the processor can
access data from memory directly
Measured in fractions of a second
called nanoseconds (ns) which is one
billionth of a second
One blink of the eye is 100 million ns; a computer
performs some operations in 10 ns
Expansion Slots and
Expansion Cards
What is an expansion slot?

An opening, or
socket, where a
circuit board can
be inserted into
the motherboard

Used to add new
devices or
capabilities to
the computer

Other terms for a circuit board include card,
expansion card, expansion board, board, adapter
card, adapter, interface card, add-in, and add-on
Expansion Slots and
Expansion Cards
What are
the uses
of
expansion
cards?
Expansion Slots and
Expansion Cards
What is Plug and Play?
The computer
automatically can
configure cards and
other devices as
you install them
Next
p. 4.24 Fig. 4-29
Expansion Slots and
Expansion Cards
What is a PC card?
Used on notebook and
other mobile computers
 Credit card-sized device
used to add capabilities
to mobile computer
 Standards developed by
Personal Computer
Memory Card
International
Click to
view Web Association (PCMCIA)

Link then click PC Cards
Next
p. 4.24 Fig. 4-30
Ports
What is a port?
Used to
connect
external
devices to the
system unit
 Port is the
interface, or
point of
attachment, to
Click to
view
the system unit
Web
Link then
click Ports  Most located
and
on the back of
Connectors
the system unit
Next

p. 4.25 Fig. 4-32
keyboard
USB
serial port
mouse
USB
printer (parallel
port)
speaker
monitor
microphone
game port
network
telephone line
in
svideo out
telephone
line out
FM reception
cable TV
Ports
What is a
connector?
Used to connect
external devices to the
system unit
 Port is the interface,
or point of attachment,
to the system unit
 Most located on the
back of the system
unit
 Gender changer is a
device that allows you
to join two connectors
that are the same

Next
p. 4.26 Fig. 4-33
power cord
keyboard
connector
USB
connector
network
connector
mouse
connector
printer
connector
monitor
connector
speaker
connector
microphone
connector
telephone line
in connector
Ports
What are the different types of connectors?
Next
p. 4.26 Fig. 4-34
Ports
What is a serial port?
Transmits one bit of
data at a time
 Used to connect
devices that do not
require fast
transmission rates
• mouse
• keyboard
• modem
 Two common types
• 25-pin
• 9-pin

Next
p. 4.27 Fig. 4-35
serial
transmission
of data
byte
representation
for number 3
(00110011)
DB-9 female
connector
DB-9 male
connector
byte
representation
for number 1
(00110001)
byte
representation
for number 5
(00110101)
Ports
What is a parallel port?



Connects devices that
can transfer more than
one bit at a time
Usually used for printers
Two newer types
byte representation for
number 1
byte representation for
number 3
byte representation for
number 5
• EPP (Enhanced Parallel
Port)
• ECP (Extended
Capabilities Port)

IEEE 1284 is a standard
that specifies how older
DB-25 male
and newer peripheral
connector
devices transfer data to
and from a computer
Next
p. 4.27 Fig. 4-36
DB-25 female
connector
Ports
What is a universal serial bus port (USB)?
Can connect up
to 127 different
peripheral
devices with a
single
connector type
 Supports newer
peripherals
 Supports hot
plugging and
Plug and Play

Next
p. 4.28 Fig. 4-37
Ports
How are multiple USB devices connected?

Daisy Chain
 USB hub
• Devices connected together • Plugs into the USB port on the
outside the system unit in a
chain
computer
• Contains multiple USB ports
Computer with
USB port
Computer with
USB port
USB
hub
device
1
device
3
Next
p. 4.28
device
2
device
1
device
4
device
2
device
3
device
4
Buses
What is a bus?



Electrical channels that allow
various devices inside the
computer to communicate with
each other
Bus width determines the number
of bits transmitted at one time
Word size determines the number
of bits the processor can interpret
and execute at a given time
Click to view Web Link
then click Buses
Next
p. 4.29 Fig. 4-39