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Tomorrow’s Technology and You 8 th Edition. © 2008 Prentice-Hall, Inc. Tomorrow’s Technology and You 8/e. Chapter 14 Systems Design and Development. © 2008 Prentice-Hall, Inc. Tomorrow’s Technology and You 8/e Chapter 14 Objectives.

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tomorrow s technology and you 8 e

Tomorrow’s Technology and You 8/e

Chapter 14

Systems Design and Development

© 2008 Prentice-Hall, Inc.

tomorrow s technology and you 8 e chapter 14 objectives

Tomorrow’s Technology and You 8/eChapter 14Objectives

Describe the process of designing, programming, and debugging a computer program.

Explain why there are many different programming languages and give examples of several of these languages.

Explain why computer languages are built into applications, operating systems, and utilities.

Outline the steps in the life cycle of an information system and explain the purpose of program maintenance.

© 2008 Prentice-Hall, Inc.

tomorrow s technology and you 8 e chapter 14 objectives continued

Tomorrow’s Technology and You 8/e Chapter 14Objectives (continued)

Explain the relationship between computer programming and computer science.

Describe the problems faced by software engineers in trying to produce reliable large systems.

Explain why software companies provide only limited warranties for their products.

© 2008 Prentice-Hall, Inc.

tomorrow s technology and you 8 e chapter 14 grace murray hopper sails on software

Tomorrow’s Technology and You 8/e Chapter 14 Grace Murray Hopper Sails on Software

Grace Murray Hopper helped chart the course of the computer industry from its earliest days.

Hopper earned a Ph.D. from Yale University in 1928 and taught math for 10 years at Vassar College before joining the U.S. Naval Reserve in 1943.

The Navy assigned her to the Bureau of Ordnance Computation at Harvard University, where she worked with Howard Aiken’s Mark I, the first large-scale digital computer.

Hopper wrote programs and operating manuals for the Mark I, Mark II, and Mark III.

© 2008 Prentice-Hall, Inc.

tomorrow s technology and you 8 e chapter 14 grace murray hopper sails on software6

Tomorrow’s Technology and You 8/e Chapter 14 Grace Murray Hopper Sails on Software

After World War II, Hopper left Harvard to work on the UNIVAC I, the first general purpose commercial computer, as well as other commercial computers

She played central roles in the development of the first compiler (a type of computer language translator that makes most of today’s software possible) and COBOL, the first computer language designed for developing business software.

Hopper’s greatest impact was probably the result of her tireless crusade against the “We’ve always done it that way” mind-set.

In the early days of computing, she worked to persuade businesses to embrace new technology.

In later years, she campaigned to shift the Pentagon and industry away from mainframes and toward networks of smaller computers.

© 2008 Prentice-Hall, Inc.

tomorrow s technology and you 8 e chapter 14 how people make programs

Tomorrow’s Technology and You 8/e Chapter 14 How People Make Programs

Programming is a specialized form of problem solving.

Problem solving typically involves four steps:

Understand the problem.

This is the most important step in the problem-solving process.

Devise a plan for solving the problem.

What resources are available and how might they be put to work to solve the problem?

Carry out the plan.

This often overlaps with the previous step.

Evaluate the solution.

Is the problem solved correctly?

Is this solution applicable to other problems?

© 2008 Prentice-Hall, Inc.

tomorrow s technology and you 8 e chapter 14 how people make programs8

Tomorrow’s Technology and You 8/e Chapter 14 How People Make Programs

The programming process can also be described as another four-step process, although in practice these steps often overlap:

Define the problem.

Devise, refine, and test the algorithm.

Write the program.

Test and debug the program.

© 2006Prentice-Hall, Inc.

tomorrow s technology and you 8 e chapter 14 how people make programs9

Tomorrow’s Technology and You 8/e Chapter 14 How People Make Programs

A teacher needs a program that is a number-guessing game

so students can learn to develop logical strategies and practice their arithmetic. In this game, the computer picks a number between 1 and 100 and gives the player 7

turns to guess the number. After each incorrect try, the

computer tells the player whether the guess is too high or too

low.

From Idea to Algorithm

Start with a statement of the problem:

© 2008 Prentice-Hall, Inc.

tomorrow s technology and you 8 e chapter 14 how people make programs10

Tomorrow’s Technology and You 8/e Chapter 14 How People Make Programs

Stepwise refinement

Initially, a problem can be divided into three parts: a beginning, a middle, and an end.

Each of these parts represents a smaller programming problem to solve.

BeginGame

Repeat Returnuntil Number isGuessed

EndGame

© 2008 Prentice-Hall, Inc.

tomorrow s technology and you 8 e chapter 14 how people make programs11

Tomorrow’s Technology and You 8/e Chapter 14 How People Make Programs

  • Begin Game
  • Display instructions.
  • Pick a number between one and 100.

2. Repeat Turn until Number is Guessed

Input guess from user. Respond to guess. End repeat.

The next refinement fills in a few details for each part:

  • End Game
  • Display end message.

© 2008 Prentice-Hall, Inc.

tomorrow s technology and you 8 e chapter 14 how people make programs12

Tomorrow’s Technology and You 8/e Chapter 14 How People Make Programs

Control structures

Control structures—logical structures that control the order in which instructions are carried out

Three basic control structures:

Sequence: group of instructions followed in order from first to last

Selection: choosing between alternative courses of action depending on certain conditions

Repetition: allowing a group of steps to be repeated several times, usually until some condition is satisfied

© 2008 Prentice-Hall, Inc.

tomorrow s technology and you 8 e chapter 14 how people make programs13

Tomorrow’s Technology and You 8/e Chapter 14 How People Make Programs

display instructions

pick a number between 1 and 100

set counter to 0

A sequence control structure

if guess < number, then say guess is too small;

else say guess is too big

A selection control structure

repeat turn until number is guessed or counter = 7

input guess from user

add 1 to counter

end repeat

A repetition control structure

© 2008 Prentice-Hall, Inc.

tomorrow s technology and you 8 e chapter 14 how people make programs14

Tomorrow’s Technology and You 8/e Chapter 14 How People Make Programs

Testing the algorithm

This round of testing is designed to check the logic of the algorithm.

Test the algorithm by following the instructions using different sets of numbers.

© 2008 Prentice-Hall, Inc.

tomorrow s technology and you 8 e chapter 14 how people make programs15

Tomorrow’s Technology and You 8/e Chapter 14 How People Make Programs

From Algorithm to Program

A simple program contains:

The program heading

The declarations and definition

The body

The programmer defines the words number,guess, and counter.

Each of these words represents a variable—a named portion of the computer’s memory.

Variables become part of the program’s vocabulary.

The program can examine and change variables.

© 2008 Prentice-Hall, Inc.

tomorrow s technology and you 8 e chapter 14 how people make programs16

Tomorrow’s Technology and You 8/e Chapter 14 How People Make Programs

Into the Computer

A text editor is an application used to enter and save a program.

Either a translator or a compiler is used to translate a program into machine language.

Translation software (or a translator), called an interpreter, translates a high-level program to machine language one statement at a time during execution.

© 2008 Prentice-Hall, Inc.

tomorrow s technology and you 8 e chapter 14 how people make programs17

Tomorrow’s Technology and You 8/e Chapter 14 How People Make Programs

Syntax errors—violations of the grammar rules of a programming language

Often flagged automatically as soon as they’re typed into the editor

Logic errors—problems with the logical structure of a program

Cause differences between what the program is supposed to do and what it actually does

Not always as easy to detect

© 2008 Prentice-Hall, Inc.

tomorrow s technology and you 8 e chapter 14 how people make programs18

Tomorrow’s Technology and You 8/e Chapter 14 How People Make Programs

A compiler translates an entire high-level program to machine language before executing the program.

A typical compiler is an integrated programming environment, containing

A text editor

A compiler

A debugger to simplify the process of locating and correcting errors

A variety of other programming utilities

© 2008 Prentice-Hall, Inc.

tomorrow s technology and you 8 e chapter 14 programming languages and methodologies

Tomorrow’s Technology and You 8/e Chapter 14 Programming Languages and Methodologies

Machine Language and Assembly Language

Machine language: the native language of a computer

Instructions for the four basic arithmetic operations, for comparing pairs of numbers, and for repeating instructions, etc. are all binary.

Instructions, memory locations, numbers, and characters are all represented by strings of zeros and ones.

Assembly language: functionally equivalent to machine language but easier for people to read, write, and understand

© 2008 Prentice-Hall, Inc.

tomorrow s technology and you 8 e chapter 14 programming languages and methodologies20

Tomorrow’s Technology and You 8/e Chapter 14 Programming Languages and Methodologies

An assembler translates each statement of assembly language into a corresponding machine language statement.

© 2008 Prentice-Hall, Inc.

tomorrow s technology and you 8 e chapter 14 programming languages and methodologies21

Tomorrow’s Technology and You 8/e Chapter 14 Programming Languages and Methodologies

High-Level Languages

High-level languages fall somewhere between natural human languages and precise machine languages.

Examples: C++, Java, Basic, FORTRAN, COBOL, Python, Pascal, LISP, ADA, PROLOG

These languages are easier to write and debug and are transportable between machines.

© 2008 Prentice-Hall, Inc.

tomorrow s technology and you 8 e chapter 14 programming languages and methodologies22

Tomorrow’s Technology and You 8/e Chapter 14 Programming Languages and Methodologies

Structured Programming

Structured programming is a technique that makes the programming process easier and more productive.

A program is well-structured if:

It’s made up of logically cohesive modules.

The modules are arranged in a hierarchy.

It’s straightforward and readable.

© 2008 Prentice-Hall, Inc.

tomorrow s technology and you 8 e chapter 14 programming languages and methodologies23

Tomorrow’s Technology and You 8/e Chapter 14 Programming Languages and Methodologies

Object-Oriented Programming

In object-oriented programming (OOP), a program is not just a collection of step-by-step instructions or procedures, but a collection of objects.

Objects contain both data and instructions and can send and receive messages.

C++ and Java are today’s most popular object-oriented languages.

© 2008 Prentice-Hall, Inc.

tomorrow s technology and you 8 e chapter 14 programming languages and methodologies24

Tomorrow’s Technology and You 8/e Chapter 14 Programming Languages and Methodologies

With OOP technology, programmers can build programs from prefabricated objects in the same way builders construct houses from prefabricated walls.

Example: An object that sorts addresses in alphabetical order in a mailing list database can also be used in a program that sorts hotel reservations alphabetically.

© 2008 Prentice-Hall, Inc.

tomorrow s technology and you 8 e chapter 14 programming languages and methodologies25

Tomorrow’s Technology and You 8/e Chapter 14 Programming Languages and Methodologies

Visual Programming

Visual programming tools enable programmers to create large portions of their programs by drawing pictures and pointing to on-screen objects.

The process eliminates much of the tedious coding of traditional programming.

Apple’s HyperCard was probably the first popular example of a visual programming environment.

HyperCard includes a programming language called HyperTalk.

A HyperCard programmer doesn’t need to know HyperTalk to create working applications.

Microsoft’s Visual BASIC includes many of the ideas and tools of object-oriented programming.

© 2008 Prentice-Hall, Inc.

tomorrow s technology and you 8 e chapter 14 programming languages and methodologies26

Tomorrow’s Technology and You 8/e Chapter 14 Programming Languages and Methodologies

Languages for Users

Macro languages (also called scripting languages) allow users to create programs, called macros, that automate repetitive tasks.

Microsoft Office includes a scripting variation of Visual Basic called Visual Basic for Applications (VBA).

Fourth-generation languages (4GL)use English-like phrases and sentences to issue instructions.

Called nonprocedural languages

Focus on what needs to be done, not how to do it

4GL example: the query language that enables a user to request information from a database

© 2008 Prentice-Hall, Inc.

tomorrow s technology and you 8 e chapter 14 programming languages and methodologies27

Tomorrow’s Technology and You 8/e Chapter 14 Programming Languages and Methodologies

Component Software

Component software makes it possible to construct small custom applications from software components.

It is the logical extension of object-oriented languages.

Customization is possible only if applications are programmed to allow it.

More and more software programs, including operating systems, are designed with extensibility in mind.

Such software may soon reach a level where users and managers can build their own applications.

© 2008 Prentice-Hall, Inc.

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Tomorrow’s Technology and You 8/e Chapter 14 Programming Languages and Methodologies

Extreme Programming

Programmers use a variety of languages, including C and C++, to write Web applications.

Some programming languages are particularly useful for developing Web applications:

HTML

JavaScript

Java

Perl

XML

© 2008 Prentice-Hall, Inc.

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Tomorrow’s Technology and You 8/e Chapter 14 Programming Languages and Methodologies

Many experts see a future in which PC applications will take a back seat to Web-based applications.

Web-based personal information managers, reference tools, and games are growing steadily in popularity.

Because of the distributed nature of the Web and the limited bandwidth of many Internet connections, Web- based applications present several challenges for users.

© 2008 Prentice-Hall, Inc.

slide30

Tomorrow’s Technology and You 8/e Chapter 14 Programs in Perspective: Systems Analysis and the Systems Life Cycle

Systems Development

Systems development: a problem-solving process of:

Investigating a situation

Designing a system solution to improve the situation

Acquiring the resources to implement the solution

Evaluating the success of the solution

A steering committee may be formed to decide what projects should be considered first.

Made up of people from each functional area in the organization

© 2008 Prentice-Hall, Inc.

slide31

Tomorrow’s Technology and You 8/e Chapter 14 Programs in Perspective: Systems Analysis and the Systems Life Cycle

A business organization may choose to contract, or outsource, a systems analyst from an outside consulting firm.

A systems analyst is an IT professional primarily responsible for developing and managing a system.

Outsourcing avoids the need for permanent in-house staff.

It allows an organization to hire talent for selected activities on a contract basis.

End-user development allows end users to create applications.

End-users need access to and training in the use of Web site development tools, spreadsheet and database management packages, and fourth-generation languages.

© 2008 Prentice-Hall, Inc.

slide32

Tomorrow’s Technology and You 8/e Chapter 14 Programs in Perspective: Systems Analysis and the Systems Life Cycle

Investigation

The Systems Development Life Cycle (SDLC)

The graphical “waterfall”model of the SDLC showsa basic sequential flow fromidentifying the “right things to do” to making sure that“things are done right.”

Analysis

Design

Development

Implementation

Maintenance

Retirement

© 2008 Prentice-Hall, Inc.

slide33

Tomorrow’s Technology and You 8/e Chapter 14 Programs in Perspective: Systems Analysis and the Systems Life Cycle

Investigation

  • Define the problem:
  • Identify the information needs of the organization.
  • Examine the current system.
  • Determine how well it meets the needs of the organization.
  • Study the feasibility of changing or replacing the current system.

© 2008 Prentice-Hall, Inc.

slide34

Tomorrow’s Technology and You 8/e Chapter 14 Programs in Perspective: Systems Analysis and the Systems Life Cycle

Analysis

  • During the analysis phase, the systems analyst :
  • Gathers documents
  • Interviews users of the current system
  • Observes the system in action
  • Generally gathers and analyzes data to understand
  • the current system and identify new requirements

© 2008 Prentice-Hall, Inc.

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Tomorrow’s Technology and You 8/e Chapter 14 Programs in Perspective: Systems Analysis and the Systems Life Cycle

Design

Prototyping is an interactive methodology

in which the prototype is continually

modified and improved until it meets

the needs of the end-user.

Identifyrequirements.

Develop workingmodel of the system.

Develop application, install prototype forevaluation by end-users,begin new prototype, orabandon application.

Makeany

necessarychangesto

prototype.

Use prototype.

Evaluate featuresof prototype.

© 2008 Prentice-Hall, Inc.

slide36

Tomorrow’s Technology and You 8/e Chapter 14 Programs in Perspective: Systems Analysis and the Systems Life Cycle

Development

The systems analyst must

carefully plan and schedule

activities in the development

phase of the SDLC because

they can overlap and occur

Simultaneously.

© 2008 Prentice-Hall, Inc.

slide37

Tomorrow’s Technology and You 8/e Chapter 14 Programs in Perspective: Systems Analysis and the Systems Life Cycle

Implementation

  • Direct cutover approach
  • Parallel systems approach
  • Phase-in approach
  • Pilot approach

© 2008 Prentice-Hall, Inc.

slide38

Tomorrow’s Technology and You 8/e Chapter 14 Programs in Perspective: Systems Analysis and the Systems Life Cycle

Maintenance

The maintenance phase involves monitoring,

evaluating, repairing, and enhancing the system

throughout the lifetime of the system.

© 2008 Prentice-Hall, Inc.

slide39

Tomorrow’s Technology and You 8/e Chapter 14 Programs in Perspective: Systems Analysis and the Systems Life Cycle

Retirement

Systems are often used for many years;

but at some point in the life of a system,

ongoing maintenance is not enough.

© 2008 Prentice-Hall, Inc.

slide40

Tomorrow’s Technology and You 8/e Chapter 14 Programs in Perspective: Systems Analysis and the Systems Life Cycle

Systems Development Tools and Techniques

Data collection techniques include:

Review

Interviews

Questionnaires

Observation

Sampling

© 2008 Prentice-Hall, Inc.

slide41

Tomorrow’s Technology and You 8/eChapter 14 Programs in Perspective: Systems Analysis and the Systems Life Cycle

Modeling tools

Modeling tools are graphic representations of systems.

System flowcharts, data flow diagrams, data dictionaries, and decision tables are the most widely-used modeling tools.

© 2008 Prentice-Hall, Inc.

slide42

Tomorrow’s Technology and You 8/e Chapter 14 Programs in Perspective: Systems Analysis and the Systems Life Cycle

Computer-aided systems engineering (CASE) tools include:

Charting and diagramming tools to draw system flowcharts and data flow diagrams

A centralized data dictionary containing detailed information about all the system components

A user interface generator to create and evaluate many different interface designs

Code generators that automate much of the computer programming to create a new system or application

© 2008 Prentice-Hall, Inc.

slide43

Tomorrow’s Technology and You 8/e Chapter 14 Programs in Perspective: Systems Analysis and the Systems Life Cycle

Some CASE software packages contain tools that apply primarily to the analysis and design phases of the systems development life cycle.

Others contain tools that automate the later phases of systems development, implementation, and maintenance.

Integrated CASE tools incorporate the whole spectrum of tools to support the entire systems development life cycle.

© 2008 Prentice-Hall, Inc.

tomorrow s technology and you 8 e chapter 14 rules of thumb

Tomorrow’s Technology and You 8/e Chapter 14 Rules of Thumb

Avoiding Information Technology Project Failures

Here are six tips for information workers on how to prevent the failure of IT projects:

IT projects need executive sponsorship.

IT projects need user input.

IT projects need specifications.

IT projects need realistic expectations.

IT projects need cooperative business partners.

IT projects need open and honest communication.

© 2008 Prentice-Hall, Inc.

tomorrow s technology and you 8 e chapter 14 the science of computing

Tomorrow’s Technology and You 8/e Chapter 14 The Science of Computing

Many computer scientists prefer to call their field computing science because it focuses on the process of computing rather than on computer hardware.

Computer science includes a number of focus areas:

Computer theory

Algorithms

Data structures

Programming concepts and languages

Computer architecture

Management information systems

Software engineering

© 2008 Prentice-Hall, Inc.

tomorrow s technology and you 8 e chapter 14 the state of software

Tomorrow’s Technology and You 8/e Chapter 14 The State of Software

Software Problems

Software errors are difficult to locate and more difficult to remove:

Errors of omission

Syntax errors

Logic errors

Clerical errors

Capacity errors

Judgment errors

© 2008 Prentice-Hall, Inc.

tomorrow s technology and you 8 e chapter 14 the state of software47

Tomorrow’s Technology and You 8/e Chapter 14 The State of Software

Software Solutions

Computer scientists and software engineers are responding to reliability and cost problems on five main fronts:

Programming techniques

Programming environments

Program verification

Clean-room programming

Human management

It could well be that by the close of the twenty-first century, a new form of truly accessible programming will be the province of everyone, and will be viewed like writing, which was once the province of the ancient scribes but eventually became universally accessible.

—Michael Dertouzos, in What Will Be

© 2008 Prentice-Hall, Inc.

tomorrow s technology and you 8 e chapter 14 the state of software48

Tomorrow’s Technology and You 8/e Chapter 14 The State of Software

Software Warranties

In the past, consumer software manufacturers provided no warranties for their products.

Today some manufacturers will give money back if the software cannot be installed on the computer.

No software manufacturer will accept liability for harm caused to you or your business by errors in software.

Why?

Additional precautions needed to make the software work better would inflate the cost and extend the time needed for development.

Only large companies would be able to sustain the pressure of such a scenario.

© 2008 Prentice-Hall, Inc.

tomorrow s technology and you 8 e chapter 14 the state of software49

Tomorrow’s Technology and You 8/e Chapter 14 The State of Software

The Future of Programming?

Programming languages will continue to evolve in the direction of natural languages, like English.

The line between programmer and user is likely to grow hazy.

Computers will play an ever-increasing role in programming themselves.

Future programming tools will have little in common with today’s languages.

When future computer historians look back, they’ll marvel at how difficult it was for us to instruct computers to perform even the simplest actions.

© 2008 Prentice-Hall, Inc.

tomorrow s technology and you 8 e chapter 14 lesson summary

Tomorrow’s Technology and You 8/eChapter 14Lesson Summary

Computer programming is a specialized form of problem solving that involves developing an algorithm for solving a problem.

Most programmers use stepwise refinement to repeatedly break a problem into smaller, more easily solvable problems.

Computer languages have evolved through several generations, with each generation easier to use and more powerful than the one that came before.

Most modern languages encourage structured programming.

© 2008 Prentice-Hall, Inc.

tomorrow s technology and you 8 e chapter 14 lesson summary continued

Tomorrow’s Technology and You 8/e Chapter 14Lesson Summary (continued)

Many applications contain built-in macro languages, scripting languages, and query languages that give programming power to users.

Object-oriented programming (OOP) tools enable programmers to construct programs from objects with properties and provide the ability to send messages back and forth; many believe that OOP represents the future of programming.

Programs are part of larger information systems.

© 2008 Prentice-Hall, Inc.

tomorrow s technology and you 8 e chapter 14 lesson summary continued52

Tomorrow’s Technology and You 8/e Chapter 14Lesson Summary (continued)

Computer scientists are responsible for the software tools and concepts that make all other software development possible.

One of the most challenging problems facing computer science is the problem of software reliability.

As more and more human institutions rely on computer systems, it is becoming increasingly important for computer scientists to find ways to make software that people can trust.

© 2008 Prentice-Hall, Inc.

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