- Slides: 17
Global Applications CS 105
Introduction • The growth in computer speed, power, and pervasiveness took even the experts by surprise. – I think there is a world market for maybe five computers — Thomas Watson, chairman of IBM 1943 – Where a calculator like the ENIAC is equipped with 18, 000 vacuum tubes and weighs 30 tons, computers in the future may have only 1, 000 vacuum tubes and perhaps weigh 1. 5 tons – Popular Mechanics, ca. 1947 – There is no reason anyone would want a computer in their home – ken Olson, president, chairman and founder of Digital Equipment Corp. , 1977
History and Technology • In the cold war days of 1960 s, the U. S. Department of Defense decided the country needed a national network connecting the scores of government and research computers. • The network had to be decentralized. • If one computer went down, the rest of the system would adapt by passing messages around the inactive site. • The Addressing System that we are using today in Internet was invented at that time.
Internet • What later become known as Internet was born as ARPANET in 1969 connecting four host Computers at UCLA, UCSB, Univ. of Utah and Stanford. • Internet: Network of networks.
How does it work? • • IP Address Message Packets. Why? Format of Packets. TCP (Transmission Control Protocol) DNS (Domain Name Server) Responsibilities of TCP vs. IP
E-Mail • Originally, email was thought to be nothing more than a minor feature, but email grew to be a large source of traffic on the Net. • SMTP (Simple Mail Transfer Protocol) • Alice sends an E-mail to her friend Bob.
E-Mail • Email is faster than the postal mail, but slower than talking over the phone or conversing in person. • Any new technology brings with it a set of social consequences that are determined by the nature of the technology itself. • We have no way of verifying the person who sends the email. • Internet robots can collect email addresses. • Social consequences eventually bring about laws governing acceptable and unacceptable behavior.
E-Mail • Different mail client program: – Unix: pine – Web-based email systems – Store messages in the remote server or download messages into local drive. • Email messages can be plain ASCII text or HTML format. – HTML can include text, pictures, and links to web pages. – HTML email can carry a Web bug: an invisible piece of code that silently notifies the sender about the user’s information.
Mailing List • Mailing lists enable you to participate in email discussion groups on specialinterest topics. • Lists can be small and local, or large and global. • They can be administered by a human being or automatically administered by programs.
E-Mail • Don’t write something in E-mail which you don’t want to be appeared some where else. • Don’t broadcast email you receive unless you first have the sender’s permission.
World Wide Web • www consists of a vast number of computers connected to internet. These computers all have software, known as browsers, that allows them to send and receive documents according to a protocol known as the Hypertext Transfer Protocol (HTTP). • Hypertext ?
Factors in Web Growth • Easy to use • Easy to Search • Easy to make a webpage
HTML • A webpage is described as an ordinary text document containing a number of html tags. The document is called HTML document. • Tags are sequence of characters which are interpreted in special ways specifying format of the text, links, images, sound and so on. • HTML (Hypertext Markup Language)
HTML • A browser can read HTML document and present it as specified by the html tags. • A html document is not a WYSIWYG. • Example • We have more on this in next module.
Other Applications • Blog – Is information that is instantly published to a Web site. Blog scripting allows someone to automatically post information to a Web site. Many people will read it and they may post responses.
Other Applications • Instant Messaging: real time communication • It is synchronous communication. • Email and newsgroups are asynchronous: sender and receiver do not have to log on at the same time.
Other Applications • Voice over IP (also called Vo. IP, IP Telephony, Internet telephony, and Digital Phone) is the routing of voice conversations over the Internet or any other IP-based network.