introduction to computers and programming lecture 1

Introduction to Computers and Introduction to Computers and ProgrammingProgramming

Lecture 1: Lecture 1: administrative details and an administrative details and an

introduction to computersintroduction to computers

Professor: Evan KorthProfessor: Evan KorthNew York UniversityNew York University

Road Map for TodayRoad 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 6 and Liang 7: chapter 1.1 – 1.4, 1.6 - 1.7– (most of today’s material is not in the book)

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Course PrerequisitesCourse 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.

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Course DescriptionCourse 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.

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What the class is really aboutWhat the class is really about

There are two main goals of this course:1. Basics of Java2.Core Concepts of Programming Languages

plus3.Learn the Principles of Software Development

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1. Learn the Basics of Java 1. Learn the Basics of Java ProgrammingProgramming 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.

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For ExampleFor 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!)

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2. Learn the Core Concepts of all 2. Learn the Core Concepts of all Programming LanguagesProgramming Languages There are many programming languages

available: Pascal, c, Java, Ada, Perl and Python. 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

An Example: For LoopsAn 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 Python.

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3. Learn the Principles of 3. Learn the Principles of Software DevelopmentSoftware 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.

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Administrative MattersAdministrative Matters

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Course Web SiteCourse Web Site Course web site is available at: http://www.cs.nyu.edu/courses/fall09/V22.0002-002/index.htmlWeb 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

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http://www.cs.nyu.edu/courses/fall09/V22.0002-002/index.html

http://www.cs.nyu.edu/courses/fall09/V22.0002-002/index.html

Class mailing listClass mailing list First assignment is to join it. Do it today! Go to:http://cs.nyu.edu/mailman/listinfo/v22_0002_002_fa09 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.

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http://cs.nyu.edu/mailman/listinfo/v22_0002_002_fa09

http://cs.nyu.edu/mailman/listinfo/v22_0002_002_fa09

Course Text BookCourse Text Book Introduction to Java

Programming (7th Edition) Brief Version

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!

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SoftwareSoftware For the course, you may use any IDE you are

comfortable using. I will use one or more of the following in the classroom:– Eclipse– JCreator (Note: this IDE has no debugger)– Netbeans

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.

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GradingGradingYour 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!

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homeworkhomeworkTen 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 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)

Back up your work. Computer crashes or lost programs are not valid excuses for not handing in an assignment.

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A Word About CheatingA Word About CheatingFor the purposes of this class, cheating is

defined as by the CS Department’s academic integrity policy– 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.

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http://cs.nyu.edu/web/Academic/Undergrad/academic_integrity.html

Student CivilityStudent CivilityIn 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!

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Help is always availableHelp is always available Option 1: Come to my Office Hours

– Tuesday, 3:30 – 4:30; Thursday, 3:30 – 4:30 (I may change the time of my office hours)

– Location: Room 319 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.

Option 3: lab tutors – see website for details Option 4: e-tutor – see website for details Option 5: College Learning Center Tutors

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IntroductionIntroductionThe 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

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What Is a Computer?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)

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Computer OrganizationComputer 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.

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Evolution of Operating SystemsEvolution of Operating SystemsBatch processing

– One job (task) at a time– Operating systems developed

Programs to make computers more convenient to use

Switch jobs easierMultiprogramming

– “Simultaneous” jobs– Timesharing operating systems


Personal Computing, Distributed Personal Computing, Distributed Computing, and Client/Server Computing, and Client/Server ComputingComputingPersonal 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.


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The boot processThe 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

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The boot process (continued)The boot process (continued)

– Boot Sector ProgramLocated in the first sector of the hard disk or other

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 commandsThen you can run your applications

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Machine Languages, Assembly Machine Languages, Assembly Languages, and High-level LanguagesLanguages, 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 BASEPAYADD OVERPAYSTORE GROSSPAY


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Machine Languages, Assembly Machine Languages, Assembly Languages, and High-level LanguagesLanguages, 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.


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Some Procedural High-level Some Procedural High-level LanguagesLanguagesOther high-level languages

– FORTRAN Used for scientific and engineering applications

– COBOL Used to manipulate large amounts of data

– Pascal Intended for academic use


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The Key Software Trend: The Key Software Trend: Object TechnologyObject 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


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History of JavaHistory of JavaA 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”.

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History or Java (continued)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

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Characteristics of JavaJava is simpleJava is object-orientedJava is distributedJava is interpretedJava is robustJava is secureJava is architecture-neutralJava is portableJava’s performanceJava is multithreadedJava is dynamic

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Basics of a Typical Java Basics of a Typical Java EnvironmentEnvironment

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


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Typical Java Typical Java environmentenvironment

PrimaryMemory

.

.

.

.

.

.

Disk

Disk

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

PrimaryMemory

.

.

.

.

.

.

Bytecode Verifier Bytecode verifier

confirms that all bytecodes are valid and do not violate Java’s security restrictions.

Phase 4

PrimaryMemory

.

.

.

.

.

.

InterpreterInterpreter reads bytecodes and translates them into a language that the computer can understand, possibly storing data values as the program executes.

Phase 5


Another Basic Step for Java Another Basic Step for Java ProgrammingProgrammingDebugging

– 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

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Hardware TrendsHardware 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


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