welcome to iit and cs115!. cs 115 - secs. 001 jon hanrath - 214 sb hanrath@iit.edu cs115hanrath

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Welcome to IIT and cs115!

CS 115 - Secs. 001

• Jon Hanrath - 214 SB

• hanrath@iit.edu

• www.cs.iit.edu/~cs115hanrath

• Lecture/Lab: TR 1:00 P.M. –4:00 P.M. SB 108

Lectures will be followed by lab time. Lab assignments are due by the end of class on Thursdays each week.

CS Intro Courses

• CS 105: 1-Semester Requiring Little or No Previous Programming Experience, Programming in C++

• CS 115-116: 2-Semester Sequence Assuming Previous Programming Experience, Programming in JAVA, Primarily CS Majors

• CS 201: 1-Semester Sequence Equivalent of CS105-CS106, Requires Previous Programming Experience, Programming in JAVA

CS 115 – Required Textbook and Lab Manual

• “Java 6 Illuminated: An Active Learning Approach” Second Edition, Anderson and Franceschi

CS 115 - Quizzes/Exams & Grading

• 2 Quizzes – Each 5% of Grade

• 2 Exams: – Exam I - Lecture Exam - 10%

– Exam II - Lecture Exam - 25%

• Final Exam - 35%

• Labs - 20%

• Must Take Final to Pass Course

CS115 Labs• Labs Assigned in Handout; on Website• Labs Consist of a Reading Assignment, and Lab

Exercises from Textbook• Lab Exercises Comprised of Exercises and

Programming Exercises (Located at End of Each Chapter in Textbook)

• Student Expected to Complete Labs *BEFORE* Lab Section Meets

• Labs Graded Either 10 (fully completed), 5 (partially completed), or 0 (not completed)

Expectations

• Attendance in Lectures and Labs

• Completion of Quizzes and Exams

• Four to Six Hours per Week on Homework

• Outside Help If Necessary

• No Cheating

• Have fun!!

Rules

• No Swearing or Other Inconsiderate Behavior

• Turn Off Cell Phones, iPads, Laptops

• Questions, Discussion, Ideas Welcome

Excuses

• If You Will Miss an Exam or Quiz, Make Arrangements **BEFORE** the Exam or Quiz Date

• Exam, Quiz Dates Already Posted

• If Emergency:– Doctor/Hospital Note– Family Problem: Contact Info for Parents

Unacceptable Excuses

• Slept Late• Felt Sick• I’m Just a Freshman• Roommate Ate My Alarm

Clock/Textbook/Underwear• Missed Bus• Had a Game/Match/Practice• Didn’t Know When Exam/Quiz Was• If Any of Above Happen, Get to Class As SOON as

Possible!!!

CS 115 - Ethics

• Exams:– Closed Book, Closed Notes, Closed Everything– Nothing in Ears (mp3 players, cell phones,

etc.)

• Labs Should Be Done Independently

CS 115 – Where to Get Help

• www.cs.iit.edu/~cs115hanrath

• Internet: Search for “JAVA tutorial”, or “JAVA help”

• GET HELP EARLY RATHER THAN LATER!!!

CS 115 – Web Page

• http://www.cs.iit.edu/~cs115hanrath

• Click on Syllabus– Weekly Assignments– Quiz and Exam Dates– Lecture Slides– Other Course Information

CS115 Labs (Cont)

• All Labs Assigned from Textbook (Anderson and Franceschi)

• Work on Labs on Personal PC, or Campus Computers

• Save .java File(s) to Floppy or flash drive, or send to yourself in email and Bring to Lab Section for Discussion and Questions

• Hand in assignments by end of class Thursday

Course Philosophy

• Computer Science Side– Problem Solving– Logical Thought– Programming in JAVA

• “Real World” Side– Human Nature– Corporate World– Surviving during and after College

Problem Solving

• CS 115 Develops Logic Skills to Solve Problems by Writing a Program

• A Program is a Problem Solving Tool

• Computers Follow Instructions Given to Them

• Computers Do Not Have “Intuition”

• Computers Do Not Make Decisions “on Their Own”

Why Use a Program?

• Computers Perform Tasks Many Times Faster than a Person

• Computers Are More Consistent than a Person

• Computers Can Work 24-7

Terminology• Source Code: the Original Problem-Solving, Logical

Solution Written in a Programming Language (e.g. JAVA, .java file)

• Interpretation: Converting source code into common language (.class file)

• Compiling: the Action of Turning the Source Code into a Format the Computer Can Use

• Linking: the Action of Bringing in Already Written Code (Libraries) for Use in a New Program

• Executable: the Result of Compiling and Linking a Source Program; the “.exe” file that the Computer Can Run

JAVA Required Elements

• Every JAVA Program Must Have:public class MyProgram

{ public static void main( String [ ] args)

{

}

}

Your First Program// Jon Hanrath

// CS115

// Section 042public class MyProgram

{ public static void main( String [ ] args)

{ System.out.println(“Hello World!!”); System.exit(0);

}

}

• Write Pseudocode (Design)

• Translate Pseudocode into JAVA Source Code

• Edit Code

• Compile

• Link

Writing a JAVA Program

• Every Programmer’s Way of Writing Down Steps in Solving a Problem

• Steps in Creating Pseudocode:– Understand the Problem– Decide How to Solve the Problem– Write the Solution Using a Logical Sequence of

Statements

• Design Issues Apply to almost ANY Vocation

What Is Pseudocode?

Writing Source Code

• Source Code Is the Actual Program Code that Will Run Once Compiled and Linked

• Pseudo Code Should Be Easily Translated into Source Code

Compiler

• Converts Source Code into an Object File or Machine Code

• Each Change to Source File Requires a Recompilation

• Compiler Detects Syntax Errors• Syntax Error: a Non-Proper, Not

Allowable, Sequence of Characters or Words Given a Particular Language

Syntax Errors

• Spelling Errors Examples:– Undefined Variable Name– Unrecognized Keyword

• Punctuation Errors Examples:– Missing Curly Braces– Missing Semicolons– Malformed Comments

• Syntax Errors Are Listed at Bottom of Screen When Compilation Is Complete

Syntax Errors (Cont)

• Syntax Errors Are Listed at Bottom of Screen When Compilation Is Completed

• First Error in Program May “Cause” Other Errors to Show Up

• General Rule: Fix First Error (and Any Obvious Errors); Then Recompile

Linking

• Links (Connects) Object Code with External Libraries, which Contain Functions (Already Written and Compiled Code) to Use with Another Program

Logic Errors – “Bugs”

• Also Called Semantic or Run-Time Errors• Program Compiles, but Doesn’t Produce the Expected

Results• Examples:

– Program Keeps Running Forever (Infinite Loop)– Nothing Happens– Program Output Is Incorrect– Error Message at Run Time (e.g. Dividing by 0)– Errors May Be Intermittent

• May Be Able to Find Semantic Problems with Debugger

Detecting “Bugs”

• Running Program Should Be Tested Several Times with Different Inputs

• Test Plan – Series of tests (e.g., inputs) that have predetermined expected outputs.

• Running Program Should Be Tested Several Times under All Potential Conditions

• When Errors Detected: Analysis Needed: Debugging Mechanism

Test Plan

• What should the Test Plan contain for a program that accepts numerical input from a user, and outputs the square of the input?

JAVA Packages/Libraries

• Over 2000 Libraries Exist

• Sometimes Called “Packages”

• Java.lang Package Automatically Imported

• Import Statements Above First Class

• Import Others with import statement

import java.util.* //import all classes

Comments• Comments: Describe a Program• // Comment to end of line• /* Comment until first occurrence of star slash */

• Difficult to Understate Importance of Good Comments• Should Be at Beginning of Program (Overall Summary)• Should Be Next to Variable Declaration Briefly

Describing Uses of Variable• Should Be Anywhere in Program Where Unobvious

Coding Is Performed

Program Format

• White Space:– Not Recognized by Compiler– Indent (e.g. 3 Spaces) for Each New Function,

Selection, or Loop

• Identifiers Used to Store Values that May Change• Every Variable Has a Type : What Kind of Value

(e.g., Integer, Floating Point Number, Character) Is Begin Stored

• Every Variable Has a Value which Is Assigned and Can Be Changed

• Every Variable Must Be Declared, which Sets Aside Memory for the Storage Location

Variables

• Declaration Normally Comes after a Function Definition Opening Curly Brace:

• public class MyProgram{ public static void main( String [ ] args) {

int num1; //variable declaration num1 = 10; // variable assignment // variable output below System.out.println(“num1 is:” + num1); }

}

• Declaration Includes Type and the Name of the Variable• All Variables Must Be Declared before Being Used

Declaring a Variable

Variables and Main Memory

int num;

num = 10;

num = 15;

<garbage>

num

10

num

Main Memory

15

num

• Storage Location of Data in a Computer• Used When a Program Is Running• “Wiped Clean” When Computer Rebooted• Byte: Basic Unit of Storage (Can Store One Letter

of the Alphabet)• Kilobyte (KB): 1000 (or 1024) Bytes (Pages of Text)• Megabyte (MB): 1,000,000 Bytes (Large Pictures)• Gigabyte (GB): 1,000,000,000 Bytes (Music Files,

Video Files)

Main Memory

• Initialization: Value Given to Variable at Declaration

• Assignment: Value Given to Variable in Execution Statement

Initialization and Assignment

public class MyProgram

{

public static void main( String [ ] args)

{

int num1 = 10; //variable initialization

System.out.println(“num1 is:” + num1);

}

}

Variable Initialization

• int: Integer Range of Typically –2,147,483,648 to 2,147,483,647 (machine and compiler dependent)

• float: Real Number (i.e., integer part, decimal part, and exponent part) Range of Typically (+/-) 10e-45 to 10e38

• double: Larger Real Number ((+/-) 10e-324 to 10e308)

• char: Character

Built-In (or Primitive) Data Types for Variables

• Can Use Letters: Remember That JAVA is Case Sensitive (e.g., NumWidgets Is Not the Same as numwidgets)

• Can Use Digits 0-9, $, and Underscore

• Cannot Start with a Digit

• Cannot Contain Spaces or Other Characters

• Cannot Use JAVA Keywords

Naming Variables in JAVA: Identifiers

• Should Use a Meaningful, Descriptive Name so that Variable’s Use Is Easily Understood:

• Examples:counter, second, minute, length, width

• Be Consistent with Case; Usually Lower Case with Upper Case for Second Part of Variable Name

• Examples:averageRainfall, totalStudentGrades, maxBuildingHeight, minPackageWeight;

Naming Variables (Cont)

• Scope: Area of a Program within which a Variable Can Be Referenced

• Variable Definitions Are Recognized in the Curly Braces in which They Were Defined

• Variables Declared Outside of Functions Are Recognized from the Point Declaration through the Rest of the Program

Variable Scope

• Constant: An Identifier that Is Initialized to a Value that Cannot Change

• Usually Declared at Top of Program using Keyword final

• Standard Naming of Constants Is to Use All Upper Case Letter with or without Underscore between Words

• All Constants Should Be Initialized• Syntax: final int MAXHT = 100;

Named Constants

• Easier to Understand• Easier to Modify• Example: Compare using Number 5000 in

Program versus Constant MAXHT

Advantages of Constants

public class MyProgram{ public static void main( String [ ] args) {

final int MAXHT = 100; ... currentHeight > MAXHT ... bridgeHeight == MAXHT ... bridgeHeight + newAddition >= MAXHT

... // used MAXHT 223 times in this program } }

Named Constants

• Constants Whose values Are Already Known:Characters (Specified Inside Single Quotes):

‘A’ , ‘a’ , ’5’ , ’ ‘ , ’\n’ (newline) , ’\0’ (NULL Character)

Integers:10, 1345, -34

Float or Double:2.3, -45.18, 10.6e6

String (Specified Inside Double Quotes):“HELLO” , “What a great deal.” , “5”

Literal Constants (Values)

• Also Known as I/O • Output : System.out.println(“Hello World!!”);

• Input (Scanner): import java.util.Scanner;Scanner scan = new Scanner(System.in);scan.nextInt();scan.nextFloat();scan.nextDouble();scan.next(); //String to whitespacescan.nextLine(); // String to end of line• All JAVA Statements End in Semicolon (;)

Input and Output

import java.util.Scanner;public class MyProgram{

public static void main( String [ ] args){

Scanner scan = new Scanner(System.in); int numEntered; System.out.print(“Enter an integer:”); numEntered = scan.nextInt();System.out.println(“You entered: “ + numEntered); }}

Input and Output Example

• Strings in java.lang package

• Java.lang imported automatically

Characters and Strings

• Declaration:String yourName;

• Assigning a Value to a String: yourName = “A. Goose”;

• String Constants (Values) Must Be Enclosed in Double Quotes

JAVA Strings

import java.util.Scanner;public class MyProgram{

public static void main( String [ ] args){

Scanner scan = new Scanner(System.in); String lastname; System.out.print(“Enter last name:”); lastname = scan.next();System.out.println(“You entered: “ + lastname); }}

Input String Example

Expressions• Expression: A Sequence of One or More

Identifiers and Operators that Evaluates to a Value• Operator: A Symbol Expressing a Way to

Modify a Value or Values (e.g., + for Addition)• Operand: A Value Being Modified by an

Operator• Example Expressions:

5

currentHeight

currentHeight + 10

Arithmetic Expressions

• Standard Arithmetic Operations Can Be Performed: Addition, Subtraction, Multiplication, Division

• Standard Arithmetic Operators Can Be Used for These Operations: +, -, *, /

• Others: % - “Modulo (Mod)” – Remainder after Integer Division -- Decrement (Subtract 1)++ Increment (Add 1)

Order of Operations

• Precedence: Level of Importance of OperationsMultiplicative Operators Have Higher Precedence than

Additive Operators:*, /, % Higher+, - Lower

• Associativity: Order of Operation for Equal Level PrecedenceMost Operators Have Left-to-Right AssociativityUse Parentheses to Force Differing Precedence of

Operations

Know for the Quiz

• All Terms (Underlined Items)

• Variable Declaration, Initialization, and Assignment

• Constant Declaration

• Expressions

• Operators

• Input (Scanner) and Output (System.out)

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