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CS 7: Introduction to Computer Programming

CS 7: Introduction to Computer Programming. Java and the Internet Sections 1.4-1.6,2.1. Review. What are the 3 control structures? Project 1 handed out. Overview. Internet Java and the Internet Applets Java and GUIs. The Internet. Collections of Computers. Network

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CS 7: Introduction to Computer Programming

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  1. CS 7: Introduction to Computer Programming Java and the Internet Sections 1.4-1.6,2.1

  2. Review • What are the 3 control structures? • Project 1 handed out

  3. Overview • Internet • Java and the Internet • Applets • Java and GUIs

  4. The Internet

  5. Collections of Computers • Network • System for connecting ≥ 2 computers so can share resources • internet • Connection of ≥ 2 networks • Internet • The world-wide connection of computers that are accessible to the public • IntraNet • An network set up confined to a particular organization

  6. Computer Roles • Client • computer / software that gets information from another computer • Web Browser - client software to get Internet Resources • Server • computer / software that provides a service to a client • Protocol • set of rules defining how two systems communicate

  7. Application Layer Protocols • FTP • File Transfer Protocol • Moving files between computers • HTTP • HyperText Transfer Protocol • Moving hypertext between computers • HyperText - text documents with links to other text documents • FTPS, HTTPS, SSH • Secure communication

  8. What’s the address? • IP address • 32-bit address to identify computer • Each computer connected has unique IP • Ex: 130.49.222.47

  9. URLs • Uniform Resource Locator • address to resource (files or request some processing be done) from the Internet • http://www.cs.pitt.edu/~hoffmanp/cs7.html • http • protocol • www.cs.pitt.edu • Fully qualified domain name (FQDN) of server machine • Domain name servers (DNS) • convert FQDN to IP address (130.49.220.23) • ~hoffmanp/cs7.html • Path to resource on the server

  10. Internet vs. WWW • World Wide Web (WWW) - 2 definitions • set of resources that can be gotten using the HTTP protocol • set of HTTP servers ("web servers") • The WWW Works on top of the Internet

  11. Java and the Internet

  12. Java • Why use Java? • Portable • Internationalization (Unicode) • Network features • Many features and libraries promoting networking • Applets can be distributed over Internet • Designed with security in mind • Swing classes make creating GUIs easier, portable

  13. Applets • Java programs that can be embedded in HTML to run on your browser • Examples: • http://www.cse.ucsc.edu/~pohl/JBD/chap8/MiniCalcApplet.html • Games • http://java.sun.com/applets/other/Hangman/index.html • http://www.npac.syr.edu/projects/java/magic/Magic.html • Education • http://www.dhpc.adelaide.edu.au/projects/vishuman2/ • http://www.stat.sc.edu/~west/javahtml/CLT.html

  14. Difference Between Applets and Applications • Applets – little applications • Run under a browser • No main() method • Security restrictions

  15. Applet Loader • Applets loaded over the Internet are loaded by an applet class loader • Uses verifier to check there are no • Stack overflows / underflows • Invalid register accesses and store • Illegal data conversion • Uses the applet security manager

  16. Untrusted Applets • Put in a “Sandbox”. Restrictions on • Files, directories • Programs on your machine • System properties • Connecting to other computers • Windows the applet creates

  17. Trusted Applets • Trusted applets don’t have these restrictions • Trusted applets are applets that either: • Are installed on your machine • Are a signed applet with an identity you mark as trusted

  18. Graphical User Interface (GUI) • User-Interface (UI) • Text-based (DOS) • GUI (Windows XP) • Windows • Icons • Java has the Swing classes

  19. Working from home • PuTTY • F-Secure SSH Client • Windows, Mac, UNIX and new lines

  20. Getting Comfortable with UNIX

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