Computer A device capable of performing

computations and making logical decisions at speeds millions, and even billions, of times faster than human being

Process data under the control of sets of instructions called computer programs (software)

Devices (keyboard, screen, disks etc.) called hardware

Computer (Logical Unit) Input Unit ~”receiving”

Computer obtain information from various input devices (keyboard, mouse, disk, scanner, video recording, etc)

Output Unit ~”shipping” Information processed by computer and

places it on various output devices (screens, printer, speakers, disks, etc)

Computer (Logical Unit) Memory Unit ~”warehouse”

Retains information that has been entered through the input unit so that the information may be immediately available for processing. Random Access Memory, Primary Memory.

Arithmetic and Logic Unit (ALU) ~”manufacturing” Performing calculation (addition, subtraction,

multiplication, division) and decision mechanisms that allow to make comparison (equal, bigger, lesser)

Computer (Logical Unit) Central Processing Unit (CPU)

~”administrative” Computer’s coordinator and is responsible for

supervising the operation of the other section Secondary Storage Unit ~”warehouse”

Program or data nor being used by the other units are normally placed on secondary storage devices (disks) until they needed. Information in secondary storage takes longer to access than information in RAM.

Types of programming language

Machine language +1300042774 +1400593419 +1200274027

Assembly language LOAD BASEPAY ADD OVERPAY STORE GROSSPAY

High-Level language grossPay = basePay + OverTimePay

History of Internet 1962-1969

ARPAnet – intended to promote the sharing of super-computers amongst researchers in the US. Connection 56KB

ARPAnet connects 4 universities in the US; Stanford Research Institute, UCLA, UC Santa Barbara & University of Utah.

Electronic mail becomes popular

History of Internet 1970

ALOHANET developed at the University of Hawaii

1971 ARPAnet grows to 23 hosts connecting

universities and government research center 1973

ARPAnet goes international with connections to University College in London & Royal Radar Establishment in Norway

History of Internet 1979

USENET newsgroups established 1981

ARPAnet has 213 hosts 1982

The term ‘Internet’ is used for the first time 1983

TCP/IP becomes the universal language of the Internet

History of Internet 1984

Internet hosts exceeds 1,000 1987

Internet hosts exceeds 10,000 1990

The number of hosts exceeds 300,000 1991

The World Wide Web is born Now

The number of hosts is more than 10 million & more than 50 million people are connected.

World Wide Web 1990 – Tim Berners-Lee Mixes computing & communications technologies Hypermedia & hypertext concept “The basic ideas of the Web is that an information space

through which people can communicate, but communicate in a special way: communicate by sharing their knowledge in a pool. The idea was not just that it should be a big browsing medium. The idea was that everybody would be putting their ideas in, as well as taking them out. This is not supposed to be a glorified television channel Also everybody should be excited about the power to actually create hypertext. Writing hypertext is good fun, and being with a group of people writing hypertext and trying to work something out, by making links is a different way of working” ~ Tim Berners-Lee, LCS35th Anniversary, Cambridge 14 April 1999

World Wide Web CERN – European Laboratory for Particle

Physics NCSA – National Center for

Supercomputing Applications The interconnection of thousands of

WWW servers over the Internet creates what is know as the World Wide Web information space, World Wide Web hyperspace or sometimes cyberspace.

Breakthrough of WWW

Abolition of centralized information store Unambiguously locate distributed

documents. Location mechanism permitted geography-independence paradigm

Uniform interface presented to users that hides the details of formats and the protocols involved in transferring the documents

The basic ideas of the WWW

Anybody can create a document & insert it in the web

Locating the documents world-wide: a uniform method ~Uniform Resource Locator (URL)

A uniform user interface Access to any database The support of transactions

Anybody can create a document & insert it in the web

No centralized authority “Anyone can be the author of a World

Wide Web document. Anyone can make reference to any other document. Anyone can contribute the result of his or her authorship to the World Wide Web interlinked hyperspace”

Disadvantage – Chaos Advantage – everybody responsible for

maintaining their own information

Locating the documents world-wide: a uniform method

Document address called Uniform Resource Locators (URL)

References where and how to find a document

2 important information in URL: Where is the end-system (host) for the

document Mechanism to access or transfer it

A uniform user interface Simple to use Exploration way Incompatibilities between data Networking – data transfer

Access to any database

Any database, not only those specially prepared as WWW document, may be accessed from and presented via standard WWW client systems. It is therefore not necessary to rewrite existing information bases to make them available through WWW.

The support of transaction Input information to remote systems Using form E-commerce

The WWW Protocols 3 major components

Uniform Resource Locator (URL)• Specify how to get a document using name not IP

address HyperText Markup Language (HTML)

• Format for specifying simple logical structures (headers, paragraphs, lists, highlighting, etc.) and hypertext links.

HyperText Transfer Protocol (HTTP)• Transfer of documents attached to WWW hyperlinks

The WWW Protocols (continue) “The World-Wide Web technical concept

lies in the use of hypermedia principles, where the idea of geography independence has been implemented by the definition of a syntax to locate documents anywhere on the Internet (the Uniform Resource Locator) and the specification of a simple document format (the HyperText Markup Language) to describe simple structures and hyperlinks”.

WWW fields of application Dissemination of human memory and culture Help to people with special needs Education Commerce (marketing, advertising, remote

shipping) Governmental or adminitrative information and

transactions Medical information and information Computer-supported cooperative work Electronic publishing Electronic virtual library

Browsers A browser is an application program that

provides a way to look at and interact with all the information on the World Wide Web

Mosaic - first widely-distributed graphical browser or viewer for the World Wide Web

Netscape Navigator Microsoft Internet Explorer Lynx – text only browser for UNIX and VMS users Opera

Issues with the WWW Link fossilization

Changes in computer name Linked documents moved to other host computer Outdated target document

Network overload User are not always warned of document sizes

before activating a link Users and authors are not always conscious of

the network implications The same document may be transferred many

times between a server and a client site

Issues with the WWW (cont.)

Free access to human knowledge versus profit-oriented information business Thousands of public and private

educational, research, scientific, technical and cultural information which are free of charges. The issue is: can the Web continue evolving as a seemingly free-of-charges resource?

WWW good design: Issues Usability (user-friendliness) Technological availability Target audience Download times Images Sound Colors Information structured Internalization