2. Introduction to Computers and Programming Lecture 1: administrative details and an introduction to computers Professor: Evan Korth New York University

3. Road Map for Today Welcome to Introduction to Computers and Programming! Course Description –What material will we cover? –What am I getting myself into? Administrative Issues –Course Web Page, Text Book, Exams, Office Hours, Homework, Grading, Cheating Policy, etc. Syllabus History of Computers Intro. to Programming Languages and Java Reading (Liang 5): chapter 1.1 – 1.4, 1.6 - 1.8 –(most of today’s material is not in the book) 2

4. Course Prerequisites Prerequisites: –No prior programming experience required (Really) Who should be taking this course: –students who want to switch to a computer science major –students who want a computer science minor or a computer applications minor –students who are just interested in programming. Who should NOT be taking this course –Students trying to get out of taking a math requirement. This class may be more difficult than the math you are trying to avoid. You must get a c or better in this class to take further computer science classes. 3

5. Course Description Official Description: Elementary introduction to programming. The characteristics of computers are discussed and students design, code, and debug programs using a high level programming language. 4

6. What the class is really about There are three main goals of this course: 1. Basics of Java 2. Core Concepts of Programming Languages 5

7. 1. Learn the Basics of Java Programming Java is a popular programming language, widely used in industry. We will learn all the specifics of how to program in Java. This includes all the peculiar rules that are specific to Java. We will cover the fundamentals: Variables, Arithmetic, If / Else, For Loops, While Loops, Arrays, Methods, etc. 6

8. For Example /* Sample Java Program */ public class Sample { public static void main (String [] args) { int i; for (i = 1; i <= 10; i++) { System.out.println ("Number: " + i); } This program counts from 1 to 10. In a few weeks, it will all make sense (I promise!) 7

9. 2. Learn the Core Concepts of all Programming Languages There are many programming languages available: Pascal, c, Java, Ada, Perl. All of these languages share core concepts. By focusing on these concepts, you are better able to learn any programming language. Hence, by learning Java, you are poised to learn other languages, such as C++ or Perl. By learning the core concepts, you are also much more marketable as you are able to learn new technologies quicker. Note: Java is an object oriented programming language. However, we will not touch upon the concepts which categorize it as one. 8

10. An Example: For Loops Java has a construct called a for loop that enables a program to repeat actions over and over. Most other languages also have a for loop. Hence, by learning about for loops in Java, you can easily learn for loops in C or Ada. 9

11. 3. Learn the Principles of Software Development Building high quality software is very difficult. The course presents the syntax and concepts of programming, and also presents strategies for building real software that addresses real problems. I will also try to bring my real-world industry experience to class. 10

12. Administrative Matters 11

13. Course Web Site Course web site is available at: http://www.cs.nyu.edu/courses/spring06/V22.0002- 004/index.html Web site contains the following information: –Administrative information –Course Syllabus –Homework assignments –Class notes –Class programs –Sample exams –Compiler instructions –Link to the class mailing list 12

14. Class mailing list First assignment is to join it. Do it today! Go to: http://cs.nyu.edu/mailman/listinfo/v22_0002_004_s p06 and follow the instructions All assignments and news will be sent to the class list Homework questions should be sent to the list and answered by students when possible. 13

15. Course Text Book Introduction to Java Programming (5th Edition) Available at the NYU Bookstore Book includes a CD- ROM with Java programs and other supplemental materials. Lecture notes will follow the book. Please keep up with the reading! 14

16. Software For the course, we will be using the following software: –Sun’s JDK (Java Development Kit) –The JCreator IDE (Integrated Development Environment) or –The Netbeans IDE All these products can be downloaded from the web for free. The class website has instructions on downloading and installing these programs. If you do not have your own computer, the computer labs on campus have the software. 15

17. Grading Your grade will be determined as follows: –First Midterm (20%) –Second Midterm (20%) –Homework (possible quizzes) (20%) –Final Exam (40%) Class participation will help your grade! 16

18. homework Ten points will be deducted for each class day late, with a possible maximum of 30 points being deducted. Home works will not be accepted after the third class following its due date. For each assignment that you do not hand in within the time limit, your final grade will be lowered by one letter grade ( i.e., if you are averaging a B+, but you have missed 2 home works, your final grade will be B-). Submit the program via email to the grader (more on this later) Buy a few floppy disks: For you own good you must save all programs on a disk and back them up on another disk. Computer crashes or lost programs are not valid excuses for not handing in an assignment. 17

19. A Word About Cheating For the purposes of this class, cheating is defined as: –Copying all or part of another student's homework, project or exam. –Allowing another student to copy all or part of your homework, project, or exam. –Discussing homework concepts is fine, but you must submit your own work. If you are caught cheating, you will receive an immediate FAILURE for the course. 18

20. Student Civility In an effort to make this class enjoyable for everybody… –Please be on time to class! –Please do not talk to your friends and neighbors in class! It disturbs everyone, and makes it hard to concentrate. If you have a question, just ask me! –Please turn your pagers and cell-phones off! 19

21. Getting Help Help is always available! Option 1: Come to my Office Hours –Monday, 5:00 – 6:00; Tuesday 2:00 - 3:00; Thursday, 2:00 – 3:00 (I may change the time of my office hours) –Location: Room 419 Warren Weaver Hall –I get bored when nobody visits! –If you cannot make my office hours, I will be happy to make an appointment with you. Please try to give me advance warning when you need an appointment. Option 2: Write to the class mailing list. Please do not send homework code to the list. 20

22. Introduction The purpose of this course is to teach you about computing, but particularly, programming in Java (a powerful, widely- used programming language). Why care about computers and programming? –Enabling technology –Growing field with great opportunity (read: $) –Creative outlet 21

23. 22 What Is a Computer? Computer –Performs computations and makes logical decisions –Millions / billions times faster than human beings Computer programs –Sets of instructions by which a computer processes data Hardware –Physical devices of computer system Software –Programs that run on computers  2003 Prentice Hall, Inc. All rights reserved. (modified by Evan Korth)

24. 23 Computer Organization Six logical units of computer system –Input unit Mouse, keyboard –Output unit Printer, monitor, audio speakers –Memory unit Retains input and processed information –Arithmetic and logic unit (ALU) Performs calculations –Central processing unit (CPU) Supervises operation of other devices –Secondary storage unit Hard drives, floppy drives  2003 Prentice Hall, Inc. All rights reserved.

25. 24 Evolution of Operating Systems Batch processing –One job (task) at a time –Operating systems developed Programs to make computers more convenient to use Switch jobs easier Multiprogramming –“Simultaneous” jobs –Timesharing operating systems  2003 Prentice Hall, Inc. All rights reserved.

26. 25 Personal, Distributed and Client/Server Computing Personal computing –Computers for personal use Distributed computing –Computing performed among several computers Client/server computing –Servers offer common store of programs and data –Clients access programs and data from server  2003 Prentice Hall, Inc. All rights reserved.

27. Personal Computing, Distributed Computing, and Client/Server Computing Personal computers –Economical enough for individual –Popularized by Steve Jobs and Steve Wozniak with the introduction of the Apple in 1977. –In 1981 IBM introduced the IBM personal computer using “off the shelf” components. Distributed computing –Computing distributed over networks Client/server computing –Sharing of information across computer networks between file servers and clients (personal computers)  2003 Prentice Hall, Inc. All rights reserved. 26 (modified by Evan Korth)

28. The boot process The process by which a machine comes up from rest state to the state that is usable is known as booting When the power is turned on –The CPU runs the BIOS (Basic Input / Output System) Usually located on a chip on the motherboard Runs POST (Power On Self Test) of various hardware components Loads the boot sector program 27

29. The boot process (continued) –Boot Sector Program Located in the first sector of the hard disk or floppy disk Is responsible for loading the rest of the operation system into the RAM –Operating System Once it is loaded, it configures the various hardware components Then it waits for the user to issue commands Then you can run your applications 28

30. Machine Languages, Assembly Languages, and High-level Languages Three types of programming languages –Machine languages Strings of numbers giving machine specific instructions Example: +1300042774 (these would really be in binary) +1400593419 +1200274027 –Assembly languages English-like abbreviations representing elementary computer operations (translated via assemblers) Example: LOAD BASEPAY ADD OVERPAY STORE GROSSPAY  2000 Prentice Hall, Inc. All rights reserved. 29

31. Machine Languages, Assembly Languages, and High-level Languages –High-level languages Instructions closer to everyday English –English is a natural language. Although high level programming languages are closer to natural languages, it is difficult to get too close due to the ambiguities in natural languages (a statement in English can mean different things to different people – obviously that is unacceptable for computer programming). However, this is a big research area of computer science. Use mathematical notations (translated via compilers) Example: grossPay = basePay + overTimePay Interpreter – Executes high level language programs without compilation.  2003 Prentice Hall, Inc. All rights reserved. 30 (modified by Evan Korth)

32. Some Procedural High-level Languages Other high-level languages –FORTRAN Used for scientific and engineering applications –COBOL Used to manipulate large amounts of data –Pascal Intended for academic use  2003 Prentice Hall, Inc. All rights reserved. 31

33. The Key Software Trend: Object Technology Objects –Reusable software components that model items in the real world –Meaningful software units Date objects, time objects, paycheck objects, invoice objects, audio objects, video objects, file objects, record objects, etc. Any noun can be represented as an object –Very reusable –More understandable, better organized, and easier to maintain than procedural programming –Favor modularity  2000 Prentice Hall, Inc. All rights reserved. 32

34. History of Java A group of 13 Sun employees including James Gosling started the “Green Project” in 1991 with the intention of planning for the next wave in computing. They designed the *7 which was “ an interactive, handheld home- entertainment device controller with an animated touchscreen user interface” Gosling’s contribution to the project was an entirely new processor independent language call “Oak”. 33

35. 34 History or Java (continued) To make a long story short, people at Sun decided to use this new language for the web. At the Sun World conference in May 1995, Marc Andreessen of Netscape announced an agreement to integrate Java into its browser. This meant that webpages were no longer going to be static. Over the next few years, java became very popular for writing applets (small programs included on webpages) Today in addition to writing applets, Java is used for writing large applications as well as applications for mobile devices For more on the history of Java, check out: http://java.sun.com/features/1998/05/birthday.html http://java.sun.com/features/1998/05/birthday.html

36. 35 Characteristics of Java F Java is simple F Java is object-oriented F Java is distributed F Java is interpreted F Java is robust F Java is secure F Java is architecture-neutral F Java is portable F Java’s performance F Java is multithreaded F Java is dynamic

37. 36 Basics of a Typical Java Environment Java programs normally undergo five phases –Edit Programmer writes program (and stores program on disk) –Compile Compiler creates bytecodes from program –Load Class loader stores bytecodes in memory –Verify Verifier ensures bytecodes do not violate security requirements –Execute Interpreter translates bytecodes into machine language  2003 Prentice Hall, Inc. All rights reserved.

38. 37 Typical Java environment Primary Memory............ Disk Editor Compiler Class Loader Program is created in an editor and stored on disk in a file ending with.java. Compiler creates bytecodes and stores them on disk in a file ending with.class. Class loader reads.class files containing bytecodes from disk and puts those bytecodes in memory. Phase 1 Phase 2 Phase 3 Primary Memory............ Bytecode Verifier Bytecode verifier confirms that all bytecodes are valid and do not violate Java’s security restrictions. Phase 4 Primary Memory............ Interpreter Interpreter reads bytecodes and translates them into a language that the computer can understand, possibly storing data values as the program executes. Phase 5  2003 Prentice Hall, Inc. All rights reserved.

39. Another Basic Step for Java Programming Debugging –Check program execution and output to ensure program compiles and runs as expected –If it doesn’t, make corrections in the edit phase and repeat the remaining steps 38

40. Hardware Trends Every year or two the following approximately double: –Amount of memory in which to execute programs –Amount of secondary storage (such as disk storage) Used to hold programs and data over the longer term –Processor speeds The speeds at which computers execute their programs  2003 Prentice Hall, Inc. All rights reserved. 39

41. 40 Upcoming schedule Today: introduction Thursday (1-19): Our first Java Program Tuesday (1-24): lab visit (This is our one class day in the lab for the entire semester. We will make sure everyone knows how to use the compiler to compile and execute programs) Thursday (1-26): variables and input (back in this classroom)