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Introduction to Computing

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Introduction to Computing ­ CS101
VU
LESSON 28
INTRODUCTION TO THE INTERNET
During the Last Lecture
(Computer Networks)
We looked at the role of networks in computing
We looked at several different types of networks
We familiarized ourselves with networking topologies and protocols
Computer Network
Multiple computers that are connected together to share information and other resources
Types of Computer Networks according to the network access policy
Private
Public
Types of Computer Networks
according to the distance between nodes
LAN: Local Area Network
WAN: Wide Area Network
Network Topologies
The pattern in which computers are connected to form a network
Popular patterns:
­Point-to-point
­Star
­Bus
­Ring
Networks are also formed by combining 2 or more of these 4 basic patterns
Networking Protocols
Networks use protocols, or rules, to exchange information through shared channels. These protocols
prevent collisions of data caused by simultaneous transmission between two or more computers. Several
protocols are available for various types of networks. Here we discuss two that are popular for LANs:
Ethernet; Token Ring
Types of Communication Channels
Wire
Wireless
Wireless (Radio) LANs Are Becoming Popular
Key benefits:
Key challenges:
­ Set-up time
­
Security & privacy
­ Set-up cost
­
Quality of service
Today's G­al:Maintenance cost
­
Cost
o
­ C t se
Introduction to oht Internet
To become able to appreciate the role of the Internet in today's computing
To become familiar with the history and evolution of the Internet
an accident!
·This car was involved in that accident
It belongs to ...
Mr. Tom Peters of Palo Alto, California
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Introduction to Computing ­ CS101
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After the accident, Mr. Peters ...
filled out a form, giving info about:
Himself
­The circumstances of the accident
­Estimated repair expenses
& then ...
1/ 7
· Mr. Peters's fax machine
2/ 7 ACME Insurance Group's server in New York
3/ 7
Bhola eServices (Pvt) Ltd's server at Davis Rd, Lahore
4/ 7
Claims processing in Lahore
5/ 7
Bhola eServices (Pvt) Ltd's server at Davis Rd, Lahore
6/ 7
ACME Insurance Group's server in New York
7/ 7
Mr. Peters's home PC
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Introduction to Computing ­ CS101
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Key Question!
Why process the insurance claim in Pakistan?
Answer: Everybody Wins!
Tom Peters
ACME Insurance
Bhola eServices
Answer: Everybody Wins!
Tom Peters
Lower premium
ACME Insurance
&
Bhola eServices
Quicker turnaround
Answer: Everybody Wins!
Tom Peters
ACME Insurance
Better margins due to 50% saving
Bhola eServices
on claim processing costs
Answer: Everybody Wins!
Tom Peters
ACME Insurance
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Introduction to Computing ­ CS101
VU
Bhola eServices
Internal rate of return (IRR)
of 60-80%
The Key Point ...
Bhola eServices (Pvt) Ltd is ...
... supplying a service
... using local, attractively-priced workers
... to a remote, overseas client
... over the Internet ... & making good money in the process!
Internet
Enables users located at far-way locations to easily share information with others located all over the
world
Enables users to easily and inexpensively communicate with others located all over the world
Enables the users to operate and run programs on computers located all over the world
The Internet is unlike any previous human invention. It is a world-wide resource, accessible to all of the
humankind.
Internet Users Worldwide
673M in 2002
1B+ in 2005
(48% wireless)
1.2M Internet users in Pakistan in 5/2000
(1% of population)
In early 2002,
54% of Australian population
51% of Singaporean population
39% of Japanese population
3% of Chinese population
Key Characteristics
Geographic Distribution
Global - reaches around the world
Robust Architecture
Adapts to damage and error
Speed
Data can travels at near `c' on copper, fiber, airwaves
Key Characteristics
Universal Access
Same functionality to everyone
Growth Rate
The fastest growing technology ever
Freedom of Speech
Promotes freedom of speech
The Digital Advantage
Is digital: can correct errors
28.1 Internet: Network of Networks
A large number of networks, interconnected physically
Capable of communicating and sharing data with each other
From the user's point view, Internet ­ a collection of interconnected networks ­ looks like a single,
unified network
28.2 Internet Networking Protocols
Communications on the Internet is controlled by a set of two protocols: TCP and IP
TCP/IP Transmission Control Protocol/Internet Protocol
Networking protocol used by all computers and networks on the Internet
Originally developed by the US DoD for Unix, but now available for most other OSes
TCP breaks down the message to be sent over the Internet into packets
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Introduction to Computing ­ CS101
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IP routes these packets through the Internet to get them to their destination
When the packets reach the destination computer, TCP reassembles them into the original message
Tools & Services Available on the Internet
Electronic mail (POP, IMAP, SMTP)
Instant messaging (ICQ, MSN)
Remote login (telnet)
File transfer (ftp)
Network news (nntp)
WWW (http)
1960's
1969 - DoD-ARPA creates an experimental network ­ ARPANET ­ as a test-bed for emerging
networking technologies
ARPANET originally connected 4 universities & enabled scientists to share info & resources across
long distances
ARPANET continued to expand throughout the 70's and 80's
1970's
Networking tools developed in the 70's include:
1972 - The National Center for Supercomputing Apps. (NCSA) develops the telnet application for
remote login, making it easier to connect to a remote computer
1973 - FTP (File Transfer Protocol) is introduced, standardizing the transfer of files between networked
computers
1980's
1983 - The TCP/IP protocols becomes the only set of protocols used on the ARPANET
This sets a standard for all networks, and generates the use of the term Internet as the net of nets
ARPANET splits into two nets to keep military & non-military network sites separate: ARPANET and
MILNET
1980's
In 1982 and 1983, the first desktop computers begin to appear
Many are equipped with an OS called Berkeley Unix, which includes networking SW, allowing easy
connection to the Internet using telnet
The PC revolution continues through the 80's, making access to computer resources & net-worked info
increasingly available to public
1985-86: NSF connects the US's six supercomputing centers together, calling it the the NSFNET, or
NSFNET backbone
To expand access to the Internet, NSF developed regional nets, which were then connected to the
NSFNET backbone
Plus, NSF supported institutions (universities, etc.) in their efforts to connect to the regional nets
1987 - NSF awards a grant to Merit Network, Inc. to operate & manage future development of the
NSFNET
Merit collaborates with IBM & MCI on R&D for fast networking technologies
1989 - The backbone network is upgraded to T1, making it able to transmit data at speeds of 1.5 Mb/s
(approx. 60 pages of text/second)
1990's1990 - The ARPANET is dissolved
1991 - Gopher is developed at the U of MN
It provides a hierarchical, menu-based method for providing & locating info on the Internet
1993 - CERN releases WWW, developed by Tim Berners-Lee
It uses HTTP and hypertext, revolutionizing the way info is presented & accessed on Internet
1993 - The NSFNET is upgraded to T3 (45 Mb/s or about 1800 pages/s)
1993-1994 - Web browsers Mosaic & Netscape Navigator are introduced
Their GUI makes WWW & Internet more appealing to the general public
1995 - NSFNET is replaced by a new architecture, called vBNS which utilizes regional networks and
Network Access Points
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Introduction to Computing ­ CS101
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Who runs the Internet?
Who owns it?
Today's Goal:
Introduction to the Internet
We looked at the role Internet plays in today's computing
We reviewed some of the history and evolution of the Internet
Next Lecture:
Internet Services
We will try to familiarize ourselves with with some of the Internet services:
­http (surfing, shopping, searching)
­eMail
­ftp
­News groups, message boards, forums
­Instant messaging
­Multimedia delivery
Keyword
Pair of parenthesis
Function `arguments' separated by
Function
commas
identifier
Function definition
function writeList( heading, words ) {
enclosed in a pair
document.write( heading + "<BR>" ) ;
of curly braces
for ( k = 0 ; k < words.length ; k = k + 1 ) {
document.write( words[ k ] + "<BR>" ) ;
}
}29.3 Function Identifiers
The naming rules for function identifiers are the same as were discussed for variable and array identifiers
29.4 Arguments of a Function
A comma-separated list of data
Arguments define the interface between the function and the rest of the Web page
Arguments values are passed to the function by value (some popular languages pass arguments `by
reference' as well)
To ensure that a function is defined before it is called up, define all functions in the HEAD portion of Web
pages
function popUp( message ) {
A function call appearing
window.alert( message ) ;
as a complete statement
}
popUp( "Warning!" ) ;
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Introduction to Computing ­ CS101
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function add( a, b ) {
c=a+b;
return c ;
}
sum = add( 2, 4 ) ;
document.write( sum ) ;
function popUp( message ) {
window.alert( message ) ;
}
popUp( "Warning!" ) ;
function add( a, b ) {
c=a+b;
return c ;
}
sum = add( 2, 4 ) ;
function popUp( message ) {
document.write( sum ) ;
window.alert( message ) ;
}
a = popUp( "Warning!" ) ;
document.write( a ) ;
What will get written by
this statement?
undefined
What would this
function add( a, b ) {
modifica-tion do?
c=a+b;
return c ;
}
document.write( add( 2, 4 ) ) ;
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Introduction to Computing ­ CS101
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What Would this Statement Do?
factorial( factorial ( 3 ) ) ;
This is termed as the
recursive
use of a function
Methods
Methods are functions
They are unusual in the sense that they are stored as properties of objects
Object: A named collection of properties (data, state) & methods (instructions, behavior)
All objects have the "name"
A collection of
property: it holds the name of
properties & methods
the object (collection)
nam
method 2
e
prop
1
prop
prop
3
5
prop
2
method 3
method 1
prop
4
29.5 Event Handlers
Special-purpose functions that come predefined with JavaScript
They are unusual in the sense that they are many times called in the HTML part of a Web page and not the
<SCRIPT> ... </SCRIPT> part
More on event handlers in a future lecture
Predefined, Top-Level or Built-In Functions
Event handlers are not the only functions that come predefined with JavaScript. There are many others.
Practically, there is no difference between predefined functions and those that are defined by the
programmer (termed as user-defined or custom functions)
There are many of them, but here we discuss only two: parseInt( ), parseFloat( )
The dictionary meaning of `Parse': To
breakdown into simpler components and
analyze
parseInt( )
Syntax: parseInt ( string )
string1 = "3.14159" ;
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Table of Contents:
  1. INTRODUCTION
  2. EVOLUTION OF COMPUTING
  3. World Wide Web, Web’s structure, genesis, its evolution
  4. Types of Computers, Components, Parts of Computers
  5. List of Parts of Computers
  6. Develop your Personal Web Page: HTML
  7. Microprocessor, Bus interface unit, Data & instruction cache memory, ALU
  8. Number systems, binary numbers, NOT, AND, OR and XOR logic operations
  9. structure of HTML tags, types of lists in web development
  10. COMPUTER SOFTWARE: Operating Systems, Device Drivers, Trialware
  11. Operating System: functions, components, types of operating systems
  12. Forms on Web pages, Components of Forms, building interactive Forms
  13. APPLICATION SOFTWARE: Scientific, engineering, graphics, Business, Productivity, Entertainment, Educational Software
  14. WORD PROCESSING: Common functions of word processors, desktop publishing
  15. Interactivity to Forms, JavaScript, server-side scripts
  16. ALGORITHMS
  17. ALGORITHMS: Pseudo code, Flowcharts
  18. JavaScript and client-side scripting, objects in JavaScript
  19. Low, High-Level, interpreted, compiled, structured & object-oriented programming languages
  20. Software Design and Development Methodologies
  21. DATA TYPES & OPERATORS
  22. SPREADSHEETS
  23. FLOW CONTROL & LOOPS
  24. DESIGN HEURISTICS. Rule of thumb learned through trial & error
  25. WEB DESIGN FOR USABILITY
  26. ARRAYS
  27. COMPUTER NETWORKS: types of networks, networking topologies and protocols
  28. THE INTERNET
  29. Variables: Local and Global Variables
  30. Internet Services: FTP, Telnet, Web, eMail, Instant messaging, VoIP
  31. DEVELOPING PRESENTATIONS: Effective Multimedia Presentations
  32. Event Handlers
  33. GRAPHICS & ANIMATION
  34. INTELLIGENT SYSTEMS: techniques for designing Artificial Intelligent Systems
  35. Mathematical Functions in JavaScript
  36. DATA MANAGEMENT
  37. DATABASE SOFTWARE: Data Security, Data Integrity, Integrity, Accessibility, DBMS
  38. String Manipulations:
  39. CYBER CRIME
  40. Social Implications of Computing
  41. IMAGES & ANIMATION
  42. THE COMPUTING PROFESSION
  43. THE FUTURE OF COMPUTING
  44. PROGRAMMING METHODOLOGY
  45. REVIEW & WRAP-UP of Introduction to Computing