Chapter 1Introduction to Object-Oriented Programming

Chapter 1 TopicsOverview of Object-Oriented ProgrammingHow is Java Code Converted into a Form that a Computer Can use?Interpreting Code vs Executing CodeCompilation, Interpretation, and ExecutionKinds of Instructions Inside the ComputerProblem-Solving Techniques

What is Computer Programming?It is the process of specifying the data types and the operations for a computer to apply to data in order to solve a problem

Programming Life Cycle Phases Problem-Solving

Implementation

Maintenance

Problem-Solving PhaseANALYZE the problem and SPECIFY what the solution must do

Develop a GENERAL SOLUTION (ALGORITHM) to solve the problem

VERIFY that your solution really solves the problem

Sample Problem

A programmer needs an algorithm to determine an employees weekly wages

How would the calculations be done by hand?

One Employees Wages During one week an employee works 52 hours at the hourly pay rate $24.75How much is the employees wages? Assume a 40.0 hour normal work weekAssume an overtime pay rate factor of 1.5

Weekly Wages, in GeneralIf hours is over 40.0, then

wages = (40.0 * payRate) + (hours - 40.0) * 1.5 *payRate

otherwise,

wages = hours * payRate RECALL EXAMPLE ( 40 x $ 24.75 ) + ( 12 x 1.5 x $ 24.75 ) = $1435.50

A class is . . .a description of the representation of a specific kind of object, in terms of data and behaviorDate classdata: month, day, yearoperations to set and return month, day, year

An Object is . . .an instance of a classa Date objectJune232004

An Algorithm is . . .instructions for solving a problem in a finite amount of time using a finite amount of data

A Program is . . .an algorithm written for a computer that defines classes of objects and orchestrates their interactions to solve a problemobjects work together to create an application (or program) that solves a problem

Employees Weekly WagesObjects: Employee, pay rate, hours worked, wagesAlgorithm: 1. Get the employees hourly pay rate 2. Get the hours worked this week 3. Calculate this weeks regular wages 4. Calculate this weeks overtime wages (if any) 5. Add the regular wages to overtime wages (if any) to determine total wages for the week

A Programming Language is . . .a language with strict grammatical rules, symbols, and special words used to construct a computer program

Code is . . .the product of translating an algorithm into a programming language instructions for a computer that are written in a programming language

Implementation Phase: TestTesting means executing (running) your program on the computer, to see if it produces correct results If it does not, check the algorithm and/or code to find the error and fix it Finding known errors is called debugging

Maintenance PhaseUse and modify the program to meet changing requirements or correct errors that show up in using itMaintenance begins when your program is put into use and accounts for the majority of effort on most programs

Programming Life Cycle Problem-Solving Analysis and Specification General Solution ( Algorithm ) Verify Implementation Concrete Solution ( Code ) Test Maintenance Use Maintain

Programming Shortcut?THINKINGCODETESTPROBLEM-SOLVING PHASEIMPLEMENTATION PHASEShortcut?AlgorithmCodeProblem

Binary Representation of DataCircuit states correspond to 0 and 1

Bit (short for binary digit) refers to a single 0 or 1 Bit patterns represent data

1 byte = 8 bits

1 KB = 1024 bytes

1 MB = 1024 x 1024 = 1,048,576 bytes

How Many Possible Digits?Binary (Base 2) Numbers use 2 digits: Just 0 and 1

Decimal (Base 10) Numbers use 10 digits: 0 through 9

Machine LanguageIs not portableRuns only on specific type of computer

Is made up of binary-coded instructions (strings of 0s and 1s)

Is the language that can be directly used by the computer

Assembly LanguagesAre machine dependent and run on only one specific type of computerAre translated into machine code by assemblers Are made up of English-like abbreviations such as LOAD, STORE, or ADD

High Level Languages Are portable Are translated into machine code by compilersInstructions are written in language similar to natural languageExamples -- FORTRAN, COBOL, Pascal, C, C++Many are standardized by ISO/ANSI to provide an official description of the language

Three C++ Program Stages

Java Portability

Windows PCrunning JVM

via compiler

via interpreter JVMSOURCEBYTECODEEXECUTABLESPayroll.javaPayroll.class

Unix boxrunning JVM

Macintoshrunning JVM

Java Bytecode

Java programming languageAchieves portability by using both a compiler and an interpreterJava compiler translates a Java program into an intermediate Bytecode--not machine language An interpreter program called the Java Virtual Machine (JVM) translates each successive instruction in the Bytecode program to machine language and immediately runs it

Basic Control StructuresA sequence is a series of statements that executes one after anotherSelection (branch) executes different statements depending on certain conditionsLoop (repetition) repeats statements while certain conditions are metA subprogram breaks the program into smaller units Asynchronous control handles events that originate outside our program, such as button clicks.

SEQUENCE Statement Statement Statement. . .

SELECTION (branch)IF Condition THEN Statement1 ELSE Statement2 Statement1 Statement Statement2Condition. . .TrueFalse

LOOP (repetition). . .FalseTrueWHILE Condition DO Statement1Condition

SUBPROGRAM (function)SUBPROGRAM1. . .SUBPROGRAM1 a meaningful collection of SEQUENCE, SELECTION, LOOP, SUBPROGRAM

ASYNCHRONOUS CONTROLEVENTEVENTHANDLER

a subprogram executed when an event occurs

Object-Oriented ProgrammingA data type is the specification in a programming language of how information is represented as data and the operations that can be preformed on the dataAn object is a collection of data values and associated operationsA class is a description of one or more like objects

More OOP VocabularyInstantiation is the process of creating an object based on the description provided by a classA package is a collection of related classes

An Object of class TimeSetIncrementWrite . . .TimeOPERATIONS DATAPrivate data:

hrs 8

mins 25

secs 42

Basic Computer Components Central Processing Unit ( CPU ) Arithmetic Logic UnitControl UnitAuxiliary StorageDeviceMemory Unit ( RAM & Registers )Peripherals

Memory UnitIs an ordered sequence of storage cells, each capable of holding a piece of data

Each memory cell has a distinct address

The information held can be input data, computed values, or program instructions

Central Processing Unit (CPU)Has two components to execute program instructions --

Arithmetic/Logic Unit performs arithmetic and logical operationsControl Unit controls the order in which instructions in the program are executed

Peripheral DevicesAre input, output, or auxiliary storage devices attached to a computerInput Devices include keyboard and mouseOutput Devices include printers, video display, LCD screensAuxiliary Storage Devices include disk drives, CD-ROM and DVD-ROM drives

Problem Solving TechniquesASK QUESTIONS -- about the data, the process, the output, error conditionsLOOK FOR FAMILIAR THINGS -- certain situations arise again and againSOLVE BY ANALOGY -- it may give you a place to startUSE MEANS-ENDS ANALYSIS -- Determine the I/O and then work out the details

More Problem Solving TechniquesDIVIDE AND CONQUER -- break up large problems into manageable unitsBUILDING-BLOCK APPPROACH -- can you solve small pieces of the problem?MERGE SOLUTIONS -- instead of joining them end to end to avoid duplicate stepsOVERCOME MENTAL BLOCK -- by rewriting the problem in your own words