cmis 102a 1 introduction introduction of java introduction to programming course goals/objectives...

CMIS 102A 1

Introduction

Introduction of Java

Introduction to Programming

Course Goals/Objectives

Grading

CMIS 102A 2

Programming Languages

A programming language is a language used to write instructions for a computer to follow

Java is one of many programming languages

Features of JavaPlatform independentOOP= Object Oriented ProgrammingApplications and applets

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Platform Independent

Platform independent: the same program can run on different computers with different operating systems or different hardware. (more later)Here are three different computers each with their own unique Hardware and Software.

X86 (IBM compatible with Windows)RISC (common in embedded systems)PowerPC (Built by Macintosh)

A program for X86 will not run on a PowerPC

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Machine languageLanguage that a computer can understand directlyConsists of only 0's and 1'sDifferent computers have different machine languages

Want to write a program in a machine language?Examples:

file size: 84KB

internet connection: 2Mbps

Measure of information:

bit (b): a 0 or 1byte (B): eight bits

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Computer Thinks in Binary

Binary (base 2) - numbers use 2 digits: JUST 0 and 1

Decimal (base 10) - numbers use 10 digits:0 THROUGH 9

Converting numbers:0 0 5 101 101 1 6 110 112 10 7 123 11 8 134 100 9 14

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Measure of Information

Bit (b; short for binary digit) either a 0 or 1

Byte (B) 1 byte = 8 bits

1 KB = 1024 bytes (2^10) 1 MB = 1,048,576 bytes (2^20) 1 GB = 2^30 ~ 10^9 1 TB = 2^40 ~ 10^12

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Assembly language (low level language)Using symbolic names for binary codesNeed an assembler to translate an assembly-language program to machine code

Example:Instruction Machine LanguageJMP 2010 00100010STO 617, 201 10001001JZ0 201 10010010

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High-level languagesCloser to a natural language; easy for human beings to read and write

Two categories:CompiledInterpreted

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Compiler (is a special SW program)A program that translates a program in a high-level language to machine codeSource program (code): program in high-level languageObject program (code): translated machine code versionCompiling a program and running a program are two different activities

Interpreter (is a special SW program)Translates and executes each instruction in the source program, one at a time

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Programming Languages Compiled

Compile once then run many times (faster)

If something changes, the whole source must be Compiled again.

Distribution problems

Interpreted Since each

instruction is translated, it’s slower.

If something changes, just that code needs to be changed.

Distribution not as hard

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How Does Java Achieve Platform-Independent?

First, a Java program is compiled into an intermediate code called byte-code

Byte-code is a common language that all computers should understandIn order to understand this byte code, a computer has to install a Java Virtual Machine (JVM)

Then, the byte code is translated into machine code and executed, one at a time, by Java byte-code interpreter

Byte-code is platform independent!

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High Levellanguage

SOURCE CODE

COMPILER forWINDOWS X86

COMPILERRISC

COMPILERPowerPC

X86Needed

Object files

RISC NeededObject Files

PowerPCNeeded

Object Files

X86OBJECT FILE

RISCOBJECT FILE

PowerPCOBJECT FILE

X86 RISC PowerPC

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JAVASource Code

JAVACOMPILER

WINDOWS X86

JAVACOMPILER

RISC

JAVACOMPILERPowerPC

X86JVM

RISCJVM

PowerPCJVM

X86 RISC PowerPC

JAVASource Code

JAVASource Code

JAVABYTECODE

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Java – Pure OOP Language

To be covered next class

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Java – Applications and Applets

Java applicationStand-alone program

CUI: console User interfaceGUI: Graphical User Interface

Java appletRun within a web browserSent across the Internet and run on a local computer

Byte-code program is sentLocal computer has to have JVM

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History of Java

Developed by James Gosling and his team at Sun Micro-system in 1991As James Gosling and Henry McGilton (1996) wrote in their white paper The Java Language Environment,

"The design requirements of Java are driven by the nature of the computing environment in which software must be deployed."

Computing environment means: World Wide Web, local area networks, intranets, embedded systems such as TV set-top boxes, PDAs, cell-phones, copy machines, and other interconnected devices. Based on C and C++

Still changing1.4.21.5.0

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Working with JAVA and JCreator

You could write JAVA programs in a text program like notepad and compile them in the command line. But this is not convenient.JCreator is a program that lets you easily:

Type the JAVA programCompile the programRun the programDebug the program** It’s a program that helps you build JAVA programs

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Working with JAVA and JCreator

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Programming

A computer program: a sequence of instructions for a computer to follow to solve a problem

Programming: the process of creating a computer program to solve a problem

A computer can do some basic operations well; it follows instructions wellBut it must be told what to doA human being comes up with the solutions

How to do programming?----next!

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STEP 1: Understand the requirementsCompany Payroll Case Study (from [1])

A small company needs an interactive program to figure its weekly payroll. The payroll clerk will input data for each employee. The input data includes employee's pay rate, and the number of hours worked that week.

The program should display the weekly pay for that employee.

The weekly pay is calculated as follows: Regular pay equals the pay rate times the number of hours worked,

up to 40 hours. If the employee worked more than 40 hours, wage equals regular

pay for 40 hours plus over time pay for hours over 40 Over time pay equals 1.5 times the pay rate times the overtime hours

These are the requirements!

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Do some examples to get a feel for the problem…note the logic you take to solve the problem

Example 1: If an employee's hourly pay rate is $30.00, and he worked 52 hours.…………………………………………Then he made ____Dollars

Example 2: If an employee's hourly pay is $10.00, and she worked 36 hours.…………………………………………Then he made ____Dollars

Example 3: If an employee's hourly pay is $20.00 and he worked 40 hours. …………………………………………Then he made ____Dollars

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Analyzing the Problem by looking at INPUT and OUTPUT

INPUT DATA OUTPUTRESULTS

Hourly payRate

Hours workedWeekly pay

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Step 2) Find an Algorithm for Calculating Weekly Pay

Repeat the following process for each employee:1. Get the employee’s hourly payRate2. Get the hours worked this week

3. Calculate Wage:If hours worked is more than 40

wage = (40.0 * payRate) + (hours - 40.0) * 1.5 *payRateElse

wage = hours * payRate

4. Display wage

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An Algorithm A set of instructions for solving a problem

Step-by-step solution Precise (same input gives same output always) A computer program is, by definition, an algorithm.

But we usually use algorithm to mean instructions expressed in English or something like English

Algorithms we've seen: Recipe Direction Manual

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Another Example (from [1])

Procedure to start your car

1. Insert the key.2. Make sure transmission is in Park (or Neutral).3. Depress the gas pedal.4. Turn the key to the start position.5. If the engine starts within six seconds, release the key to

the ignition position.6. If the engine doesn't start in six seconds, release the key

and gas peal, wait ten seconds, and repeat Steps 3 through 6, but not more than five times.

7. If the car doesn't start, call the garage

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An Exercise

Write an algorithm that gets the price and quantity of an item bought, and displays the total amount paid for that item after tax. The tax rate is fixed to be 5%.

To get started, work these: a) 5 widgets at 12.00 each. How much do you pay?b) 15 widgets at 2.00 each. How much do you pay?c) W widgets at P dollars each. How much do you

pay?

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How to Do Programming? 1) Analyzing the problem: Identifying the input data and

the output results

2) Developing the solution algorithm

3) Coding the algorithm using a specific programming language

4) Testing Running (executing) your program on the computer, to see if it produces correct results

If it does not, then you must find out what is wrong with your program or algorithm and fix (debugging)

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Structured Programming

Top-down development

Any computer program can be written using only three basic control structures:

Sequence: a sequence of instructions executed in the order they're writtenSelection: executing different instructions based on certain conditionsLoop: repeating a set of instructions while certain conditions are met

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Object-Oriented Programming

To be covered next class

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Course Goals and Objectives

Describe the development of computer programming and the main characteristics of JavaGain an understanding of the fundamentals of object-oriented programming, including classes, objects, creating objects, and using methods

Apply top-down and other techniques for algorithmic problem-solving in designing and writing computer programsApply incremental development techniques in writing complex programs

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Understand and use fundamental programming constructs such as data types and declarations, assignment statements, variables, constants, and arithmetic and logical operators

Understand and apply sequence, selection, and loop control structures in writing programs to solve common computing problems

Understand and use pre-defined classes

Create, compile, and execute Java programs to do the following:

Get input data from the user and display results to the userPerform simple arithmetic calculations, and string manipulationsPerform different tasks based on user input or results of calculations (selection)Repeat tasks (loop)

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Document programs effectively Design and use test data for validating programs

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Grading

Projects (3) 50%LABS should help complete the projects

Homework including labs (assigned but not graded)These are the ‘self-test questions’ in text

Quizzes (2) 20%Short 20 question mc t/f fill-in questions and 1 JAVA code question.

Final 30%I’ll give you a sample Final + Answers

Participation counts toward marginal casesIf your on the edge of a grade, I look at the participation

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Miscellaneous

Extra Credit. Short ans: None. 1) I have no ‘extra’ time to manage extra credit work. 2) Not a good practice as a student. The intention is good but misdirected. All military related absences or late assignments are excusable. You are the one responsible for the learning the material.Planned absences should not exceed 25% of the course.

i.e. planned vacation or military exercises should not exceed 4 classes

Never disappear from class [email protected] when dropping a course!

CMIS 102A 35

Best Way to Learn Programming?

Quotes from Bill Gates:

the best way to prepare (to be a programmer) is to write programs, and to study great programs that other people have written. In my case, I went to the garbage cans at the Computer Science Center and I fished out listings of their operating system. You've got to be willing to read other people's code, then write your own, then have other people review your code.

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Best Way to do well in class

Do the HW. Don’t just look at answers Participate in class Memorize the basic coding structures Do the projects well (50% of grade!) Differentiate the ‘interesting’ from the ‘testable’ Time Management !?!

CMIS 102A 37

Review (1)

High-level programming language

machine language

interpreter

Java

source program

object program

byte-code program

compiler

platform independent

CMIS 102A 38

Review (2)

programming

computer program

algorithm

selection

loop

sequenceinput and output

CMIS 102A 39

References

[1] Programming and Problem Solving with C++, 3rd Ed., Nell Dale, Chip Weems, Mark Headington, pp 33-37.

[2] Structured programming, http://en.wikipedia.org/wiki/Structured_programming

[3] COMPILERS, INTERPRETERS AND VIRTUAL MACHINES, http://www.homepages.com.pk/kashman/jvm.htm#_computers

cmis 102a 1 introduction introduction of java introduction to programming course goals/objectives...

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