Introduction To Programming

1. Introduction To Programming

2. About me • Prof. Lyon, • vc (203)641-6293 cell. • Fax (203)877-4187 • lyon@docjava.com • Office Hours; appt only (for now).

3. About the Book • Java for Programmers: • by D. Lyon, Pren. Hall. • Grading: • 1/3, homework • 1/3 midterm • 1/3 final

4. Homework • weekly or bi-weekly • Due on time • You loose 10 points per day late! • Midterms are due in class with a demo. • Final is due in class with a demo. • Tests are take home.

5. Course Info • Web page: • http://www.docjava.com • Distributed Computing • multiple computers working on a single task. • Network gaming • client-server • browser – web-server

6. Examples of Distributed Computing • Services provided by a server • ftp server • print server • file server • mail server • echo server • ssh server • telnet server

7. Services • Where are services listed? • /etc/services • gives you a list of “ports” • Distributed Computing is Network Computing • You study Network Programming to do Network Computing

8. Cluster Computing • Group(s) of computers that are geographically co-located. Typically central administration using a master-work paradigm.

9. Cluster Problems • hard to load balance • need benchmark • need a mechanism to register a volunteer • Configuration problem – need a compute server on every machine. • need to detect when idle.

10. Cluster Problems • Need a way to partition a problem. • I need a way to transfer jobs from one machine to another. • How do you run a program on demand? • Java Web Start!

11. Examples of Cluster Computing • File System • SETI • etc…

12. What is Java? • A programming language • A technology that supports the language

13. What is a Programming Language? • A language that can run on a computer. • An invention that helps facilitate communication. • Generally, it helps people communicate with a computer.

14. What is a Computer? • A machine that processes data. • E.g. Brain= bio-computer

15. What is a machine? • A device that transforms energy. • Computers use energy to perform information processing. • E.g., Wheel, human, brain=biological computer!

16. Can Machines Think? • Humans think that they can think. • Human brain is a kind of machine. • Therefore machines can think.

17. Example Application of A programming Language • recipe • ingredients – data structures (<-input) • procedure to follow - algorithms • results - output

18. So Java Can • Take input • Fill Data structures • Run algorithms • Generate Output

19. What is HTML? • Hypertext Markup Language • Used by a Browser • Presentation of content

20. What is a browser? • a program that decodes HTML and presents it to the user. • For example: • Explorer • Netscape • Lynx

21. What is the Internet? • a collection of local area networks. • It is often viewed using a browser.

22. What is a Computer network? • A means of communicating between computers. Computer1 Computer2

23. Internet=Internetwork • Collection of Networks • Message forwarding on a data packet net Node Computer1 Computer2

24. What is the Web? • GUI on the Internet • Can use HTML for presentation of content • Browsers decode presentation data for display

25. What is the HTML Model? • Browsers present data embedded in HTML • HTML • Images • GIF, JPEG, PNG, .... • Audio • AIFF, AU,... • PLUGINS

26. What’s a Plugin • A program that helps a browser process data. • Shockwave • RealPlayer • Quicktime

27. Java Model • Add to the number of formats we can decode. • Run the Java program automatically when we visit a web page using a browser with Java.

28. Would you run a program on Demand? • A big security risk? • Feature Limits help us to be secure. • trusted programs can do anything • untrusted programs have big limits. • no file access • no access across the net to other machine. • Other restrictions too.

29. What is a Compiler? • Is a program that inputs a programming language and outputs another programming language! • Output language is lower level than input language.

30. What is Javac? • The java compiler • Inputs java source code • outputs BYTE CODES

31. How do I run BYTE CODES? • java is the command that invokes the JVM. • java inputs BYTE CODES and RUNs them!

32. Java Environment/ Life Cycle of Java Code Java Interpreter Just in Time Compiler Runtime Environment Compile-time Environment Class Loader Bytecode Verifier Java Class Libraries Java Source (.java) Java Bytecodes move locally or through network Java Virtual machine Java Compiler Runtime System Java Bytecode (.class ) Operating System Hardware

33. Lifecycle of Java Code

34. Whats a Byte? • a collection of 8 bits

35. Primitive Data Types • What is a Data type? • It is a structured record that hold bits in a format that is defined by either the programmer or the language designer. • Eg. The bit is a data type.

36. What is a bit? • Binary Digit = bit • It is symbolized by the numbers 0 or 1. • When you use a bit to count, you use a two-state numbering system. • Binary is a BI (two) state numbering (nary) system

37. What is Binary? • Two numbered system • Generally S={0,1} • 00, 01, 10, 11 (binary) • 0, 1, 2, 3 (decimal)

38. What is Hexidecimal? • 16 symbols in a numbering system. • Generally S={0,1,2,3,4,5,6,7,8,9,A, B,C,D,E,F} • (DEAD) base 16 (hexidecimal) • (CAB) • (7F) • (FF)

39. What is Octal? • A Base 8 numbering system • 8 symbols • generally S={0,1,2,3,4,5,6,7} • (177) (10) • (7) + (1) = (10) base 8 • (10)+(7)=(17) base 8 • (17)+(1)=(20) base 8

40. What is a base? • The number of symbols in a numbering system. • Radix of a numbering system is the base

41. Why do they call it the base? • In decimal we write: 42. • 42 = 4 * 10**1 + 2*10**0 • In binary we write: 1101 • 1101 = 1 * 2 ** 3 + 1 * 2**2+0*2**1+1*2**0=8 + 4 +1=13 base 10

42. What is a primitive data type? • Is a built in (to the language) data type. • That means that the language comes with the primitive data type.

43. Why do I need a primitive data type? • Holds some value represented by bits in computer memory. • It helps with computations by storing data.

44. What is an example of a PDT? • boolean – true, false. • boolean b = true; • boolean t = false; • boolean theChairsAreHard = true; • boolean theExampleIsGettingSilly = true; • The = sign means assignment. • Variables are on the left hand side of the = sign.

45. There are 8 primitive data types. • boolean • char • SignedFixedPoint (byte, short, int, long) • SignedFloatingPoint (float, double)

46. Two types of primitive data types • Signed • Unsigned

47. Two types of unsigned data types • boolean • char • example: • char c = ‘t’; • char qwerty = ‘q’; • char thisIsGettingSilly = ‘w’;

48. What is a Java statement? • Some Java code followed by a ‘;’ • char fooBar = ‘e’;

49. How many fixed point PDTs are there? • 4, byte, short, int, long • byte uses 8 bits to store values. • short uses 16 bits • int uses 32 • long uses 64

50. What are some examples? • byte b = 127; • byte b = 128; // does not work! • bytes range from –128...127 • The most significant bit is the sign bit. • byte thisIsGettingSilly = -128;