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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