Chapter 13: Programming Languages Program Development and · Understanding Computers: Today and Tomorrow, 13th Edition 2 Learning Objectives 1. 2. 3. Understand the differences between

Understanding Computers: Today and Tomorrow, 13th Edition

Chapter 13:

Program Development andProgramming Languages

Understanding Computers: Today and Tomorrow, 13th Edition2

Learning Objectives

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Understand the differences between structuredprogramming, object-oriented programming (OOP),aspect-oriented programming (AOP), and adaptivesoftware development.Identify and describe the activities involved in theprogram development life cycle (PDLC).Understand what constitutes good program design andlist several tools that can be used by computerprofessionals when designing a program.


Learning Objectives

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Explain the three basic control structures and how theycan be used to control program flow during execution.

Discuss some of the activities involved with debugginga program and otherwise ensuring it is designed andwritten properly.

List some tools that can be used to speed up orotherwise facilitate the program development process.

Describe several programming languages in use todayand explain their key features.


Overview

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This chapter covers:The most common approaches to program designand developmentThe phases of the program development life cycle(PDLC)Tools that can be used to design and develop aprogramGood program design techniques and types ofprogram errorsCommon programming languages


Approaches to Program Design andDevelopment

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Procedural programming: An approach to programdesign in which a program is separated into smallmodules that are called by the main program or anothermodule when needed

Uses procedures (modules, subprograms): Smallersections of code that perform specific tasksAllows each procedure to be performed as manytimes as needed; multiple copies of code not neededPrior to procedural programming, programs were onelarge set of instructions (used GOTO statements)Structured programming: Goes even further, breakingthe program into small modules (Top-down design)



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Variables: Named memory locationsthat are defined for a program

Used to store the current value ofdata items used in the program



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Object-oriented programming (OOP): Programs consistof a collection of objects that contain data and methodsto be used with that data

Class: Group of objects that sharesome common propertiesInstance: An individual object in aclassAttributes: Data about the state ofan objectMethods: Perform actions on anobjectObjects can perform nontraditional actions and beeasily used by more than one program



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Aspect-oriented programming (AOP): Separatesfunctions so program components can be developedand modified individually from one another

The components can be easily reused withseparate nonrelated objects

Adaptive software development: Designed to makeprogram development faster and more efficient andfocus on adapting the program as it is being written

Iterative and/or incrementalIncludes RAD (rapid application development) andextreme programming (XP)Agile software development: Focuses on buildingsmall functional program pieces during the project


The Program Development Life Cycle (PDLC)

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Program development: The process of creatingapplication programsProgram development life cycle (PDLC): The processcontaining the five phases of program development


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Problem analysis: The problem is considered and theprogram specifications are developed

Specifications developed during the PDLC arereviewed by the systems analyst and the programmer(the person who will code the program)Goal: To understand the functions the software mustperformDocumentation: Includes program specifications(what it does, timetable, programming language to beused, etc)



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Program design: The program specifications areexpanded into a complete design of the new program

Good program design is extremely importantProgram design tools

Structure charts: Depict the overall organization ofa program

Shown in Figure 13-1Flowcharts: Show graphically step-by-stephow a computer program will process data

Use special symbols and relational operatorsCan be drawn by hand or with flowchartingsoftware



Flowcharts


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Pseudocode: Uses English-like statements to outlinethe logic of a programUnified Modeling Language(UML) Models: Set ofstandard notations forcreating business models

Widely used in object-oriented programsIncludes class diagrams,use case diagrams, etc.



Unified Modeling Language (UML) Models



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Control structure: A pattern for controlling the flow oflogic in a computer program, module, or method

Sequence control structure: Series of statementsthat follow one anotherSelection control structure: Multiple paths,direction depends on result of test

If-then-elseCase (avoids nested if-then-else statements)

Repetition control structure: Repeat series of stepsDo-whileDo-until


Control Structures



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Good program design:Is essentialSaves time

Good program design principles:Be specific

All things the program must do need to bespecified

One-entry-point/one-exit-point ruleNo infinite loops or other logic errors

Infinite loop: Series of steps that repeat foreverDesign should be tested to ensure logic is correct

Desk check; tracing tablesDocumentation: Includes design specifications


Good Program Design


Program Design Testing


Program Design Testing



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Program coding: The program code is written using aprogramming language.

When choosing a programming language, consider:Suitability to the applicationIntegration with other programsStandards for the companyProgrammer availabilityPortability if being run on multiple platformsDevelopment speed

Coding creates source code


Coding Standards

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Coding standards: Rules designed to standardizeprogramming

Makes programs more readable and easier tomaintainIncludes the proper use of comments to:

Identify the programmer and last modificationdateExplain variables used in the programIdentify the main parts of the program

Reusable code: Pretested, error-free code segments thatcan be used over and over again with minormodifications

Can greatly reduce development timeDocumentation: Includes documented source code


Comments



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Program debugging and testing: The process of ensuringa program is free of errors (bugs) and works as it issupposed to

Before they can be debugged, coded programs needto be translated into executable code

Source code: Coded program before it is compiledObject code: Machine language version of aprogramLanguage translator: Program that convertssource code to machine language



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Types of language translators:Compilers: Language translatorthat converts an entire programinto machine language beforeexecuting itInterpreters: Translates one lineof code at one timeAssemblers: Convert assemblylanguage programs intomachine language



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Preliminary debugging: Finds initial errorsCompiler errors: Program doesn’t run

Typically syntax errors: When theprogrammer has not followed the rules ofthe programming language

Run time error: Error that occurs when theprogram is runningLogic errors: Program will run but produces

incorrect resultsDummy print statements can help locate logic

errors and other run time errors


Preliminary Debugging


Preliminary Debugging



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Testing: Occurs after the program appears to becorrect to find any additional errors

Should use good test dataTests conditions that will occur when the programis implementedShould check for coding omissions (productquantity allowed to be < 0, etc.)Alpha test (inside organization)Beta test (outside testers)

Documentation: Completed program package (user’smanual, description of software commands,troubleshooting guide to help with difficulties, etc.)



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Program implementation and maintenance: Installingand maintaining the program

Once the system containing the program is up andrunning, the implementation process is completeProgram maintenance: Process of updating softwareso it continues to be useful

Very costlyDocumentation: Amended program package


Quick Quiz

1. Which approach to programming uses the concept ofinheritance?a. Proceduralb. Object-orientedc. Aspect-oriented

2. True or False: An infinite loop is an example of a logicerror.

3. A(n)______________________ is a program design tool thatshows graphically step-by-step the actions a computerprogram will take.

Answers:1) b; 2) True; 3) flowchart


Tools for FacilitatingProgram Development

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Application Lifecycle Management (ALM): Creating andmanaging an application during its entire lifecycle, fromdesign through retirement

Tools include:Requirements management: Keeping track of andmanaging the program requirements as they aredefined and then modifiedConfiguration management: Keeping track of theprogress of a program development projectIssue tracking: Recording issues such as bugs orother problems that arise during development orafter the system is in place





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Application generator: Software program that helpsprogrammers develop software

Macro recorders: Record and play back a series ofkeystrokesReport and formgenerators: Tools thatenable individuals toprepare reports andforms quickly



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Device software development tools: Assist withdeveloping embedded software to be used on devices,such as cars, ATM machines, consumer devices, etcSoftware development kits (SDKs): Designed for aparticular platform; enables programmers to developapplications more quickly and easily

Released by hardware or software companiese.g. iPhone SDK

Application Program Interfaces (APIs): Help applicationsinterface with a particular operating system

Often used in conjunction with Web sites



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Rich Internet Application (RIA): Web-based applicationsthat work like installed software programs

Desktop RIA can access local files and used withoutan Internet connectionWeb-based RIAs are commonTools to develop RIAs

Adobe AIR


Quick Quiz

1. Which of the following is not an Application LifecycleManagement (ALM) tool?

a. Requirements definition softwareb. Code generatorc. Application program interface (API)2. True or False: A software development kit (SDK) is

designed for a particular platform and allows programmersto develop applications quickly for that platform.

3. A(n) ______________________ is often used to create theforms or input screens used to input data into a program ordatabase.

Answers:1) c; 2) True; 3) form generator


Programming Languages

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Programming language: A set of rules, words, symbols,and codes used to write computer programs

To write a program, you need appropriate software forthe programming language you will be using

Categories of programming languagesLow-level languages: Difficult to code in; machinedependent

Machine language: 1s and 0sAssembly language: Includes some names andother symbols to replace some of the 1s and 0s inmachine language





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High-level languages: Closer to natural languagesMachine independentIncludes 3GLs (FORTRAN, BASIC, COBOL,C, etc.)and object-oriented languages (Visual Basic, C#,Python, Java, etc.)Visual or graphical languages: Use graphicalinterface to create programs

Fourth-generation languages (4GLs): Even closer tonatural languages and easier to work with thanhigh-level

Declarative rather than proceduralIncludes structured query language (SQL) usedwith databases


Online Video

“Introducing the Scratch Graphical Programming Language”(click below to start video)

Reminder: The complete set of online videos and video podcasts are available at:www.cengage.com/computerconcepts/np/uc13

Scratch is developed by theLifelong KindergartenGroup at the MIT MediaLab. See http://scratch.mit.edu


Common Programming Languages

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FORTRAN: High-levelprogramming languageused for mathematical,scientific, and engineeringapplications

Efficient for math,engineering andscientific applicationsStill used today forhigh-performancecomputing tasks(weather forecast)



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COBOL: Designed for business transaction processingMakes extensive use of modules and submodulesBeingphased outin manyorganizationsEvolving(COBOL.NET)



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Pascal: Created as a teaching tool to encouragestructured programming

Contains a variety of control structures used tomanipulate modules systematically



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BASIC: Easy-to-learn, high-level programming languagethat was developed to be used by beginningprogrammers

Visual Basic: Object-oriented version of BASIC; uses avisual environment



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C: Designed for system programmingC++: Object-oriented versions of CC#: Used for WebapplicationsObjective-C:For iPhone andother Appleapplications



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Java: High-level, object-oriented programming languagefrequently used for Web-based applications

Java programs are compiled into bytecodeCan run on any computer that includes Java VirtualMachine (Java VM)Can be used to write Java applets

Scroll text on Web page, games, calculators, etcIs one of the most popular programming languagestoday





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Python: Open-source, dynamic, object-oriented languagethat can be used to develop a variety of applications

Gaming, scientific, database, and Web applicationsOnly recently gaining a following



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Ruby: Open-source, object-oriented language that can beused to create general-purpose or Web applications

Uses a syntax that is fairly easy to read and write,allowing programmers to create database-driven Webapplications easily and quickly


Quick Quiz

1. An example of a high-level programming language is______________________.a. Pascalb. Assembly languagec. Machine language

2. True or False: Visual Basic is an object-oriented version ofCOBOL.

3. Java applets are small programs written in the______________________ programming language.

Answers:1) a; 2) False; 3) Java


Summary

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Approaches to Program Design and DevelopmentThe Program Development Life Cycle (PDLC)Tools for Facilitating Program DevelopmentProgramming Languages

Chapter 13: Programming Languages Program Development and · Understanding Computers: Today and Tomorrow, 13th Edition 2 Learning Objectives 1. 2. 3. Understand the differences between

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