Programming and Problem Solving — Software Engineering

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Programming and Programming and Problem Solving —Problem Solving —

Software EngineeringSoftware Engineering(Read Chap. 2)

Problem SolvingProblem Solving

5 Phases of (Simplified) Software Life Cycle:

• Problem Analysis and Specification• Design• Implementation (Coding)• Testing, Execution and Debugging• Maintenance

OCD (Object-Centered Design)

A Temperature-conversion problemA Temperature-conversion problem::

Write a program that, given a temperature in Write a program that, given a temperature in Celsius, displays that temperature in Fahrenheit. Celsius, displays that temperature in Fahrenheit.

OCD (Object-Centered OCD (Object-Centered Design)Design)

1.1. Describe the _____________ of the program.Describe the _____________ of the program.

2.2. Identify the problem’s ____________Identify the problem’s ____________ and and make a table of information about them.make a table of information about them.

3.3. Identify the problem’s _________________ Identify the problem’s _________________ and make a table of information about and make a table of information about them.them.

4.4. Organize the objects and operations into a Organize the objects and operations into a sequence of steps, called a sequence of steps, called a _________________, _________________, to solve the problem.to solve the problem.

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BehaviorBehaviorUsingOCD

A. Describe the desired behavior of the A. Describe the desired behavior of the program:program:

Our program should display program information Our program should display program information to the user and then a prompt for the to the user and then a prompt for the Celsius temperature on the screen, read thatCelsius temperature on the screen, read thattemperature from the keyboard, compute thetemperature from the keyboard, compute thecorresponding Fahrenheit temperature, and corresponding Fahrenheit temperature, and display the result, along with a descriptive display the result, along with a descriptive label on the screen.label on the screen.

These make up the ____________ in our These make up the ____________ in our problem.problem.

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Problem ObjectsProblem ObjectsB. Identify the B. Identify the nounsnouns in the behavioral description (other than in the behavioral description (other than

"non-behavioral" ones like program and user):"non-behavioral" ones like program and user):

Our program should display program informationOur program should display program information

to the user and then a prompt for the to the user and then a prompt for the

Celsius temperature on the screen, read thatCelsius temperature on the screen, read that

temperature from the keyboard, compute thetemperature from the keyboard, compute the

corresponding Fahrenheit temperature, and corresponding Fahrenheit temperature, and

display that temperature, along with a descriptive display that temperature, along with a descriptive

label on the screen.label on the screen.

UsingOCD

Information about ObjectsInformation about ObjectsDetermine a _______and a ________ (if necessary) for each object Determine a _______and a ________ (if necessary) for each object

and whether it is a ____________ or a ______________.and whether it is a ____________ or a ______________.

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UsingOCD

cout

cin

Problem Object Type Kind Name

program information text

constant

none

prompt text

constant

none

Celsius temperature real number

variable

celsius

screen output

variable

keyboard input

variable

Fahrenheit temperature

real number

variable

fahrenheit

label text

constant

none

C++ Type

?

?

double

?

?

double

?

OperationsOperations

These make up the ______________ in our These make up the ______________ in our problem.problem. 7

C. Identify the C. Identify the verbsverbs in the behavioral description: in the behavioral description:

Our program should display program informationOur program should display program information

to the user and then a prompt for the to the user and then a prompt for the

Celsius temperature on the screen, read thatCelsius temperature on the screen, read that

temperature from the keyboard, compute thetemperature from the keyboard, compute the

corresponding Fahrenheit temperature, and corresponding Fahrenheit temperature, and

display that temperature, along with a descriptive display that temperature, along with a descriptive

label on the screen.label on the screen.

UsingOCD

Information about Information about OperationsOperations

Identify the C++ ____________ to perform Identify the C++ ____________ to perform a given operation, if there is one.a given operation, if there is one.

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To compute the Fahrenheit temperature, we need to

know/find the Celsius to Fahrenheit conversion formula.

UsingOCD

OperationOperationPre-Pre-defineddefined??

C++ C++ OperatoOperato

rrLibraryLibrary

DisplayDisplay yes yes << iostream

ReadRead yes yes >> iostream

Compute the Fahrenheit Compute the Fahrenheit temperaturetemperature

?? ?? ???? ????

Celsius to FahrenheitCelsius to Fahrenheit

Formula for converting Celsius to Formula for converting Celsius to Fahrenheit:Fahrenheit:

fahrenheit = 1.8 celsius + 32

Converting the temperature thus adds Converting the temperature thus adds new objects and operations to our new objects and operations to our problem.problem.

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UsingOCD

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Information about Objects Information about Objects (Revised)(Revised)

UsingOCD

Problem Object Type Kind C++ Type Name

program information text

constant

? none

prompt text

constant

? none

Celsius temperature realnumber

variable

double celsius

screen output

variable

? cout

keyboard input

variable

? cin

Fahrenheit temperature

realnumber

variable

double fahrenheit

label text

constant

? none

conversionfactor 1.8

real number

constant

double none

conversion factor 32

integer constant

int none

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UsingOCD Information about Information about

Operations (Revised)Operations (Revised)

OperationPre-defined?

C++ Operato

rLibrary

Display yes << iostreamRead yes >> iostreamCompute the Fahrenheit temperature:Multiply two real values (1.8 and celsius)

yes * built-in

Add a real value (the result above) and an integer (32)

yes + built-in

Store a real value (the result above) in a variable

yes = built-in

AlgorithmAlgorithm

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UsingOCD

D. Organize the objects and operations into a D. Organize the objects and operations into a sequence of steps that solves the problem, sequence of steps that solves the problem, called an __________________.called an __________________.

1. Display via cout information about the program to the user.

2. Display via cout a prompt for the Celsius temperature.

3. Read the temperature from cin.

4. Compute the Fahrenheit temperature from the Celsius temperature.

5. Display via cout the Fahrenheit temperature and an informative labell..

CodingCoding

Once we have designed an algorithm, the next step is to translate that algorithm into a high level language like C++.

This involves writing instructions to

— represent the objects, and

— perform the operations

in C++.

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/* temperature.cpp converts a Celsius temperature to Fahrenheit. John Doe Lab 1 Jan. 5, 2012 CS 104X Input: A Celsius temperature Output: Corresponding Fahrenheit temperature-----------------------------------------------*/

#include <iostream> // cin, cout, <<, >>using namespace std;

int main(){

// 1. Display via cout information about the // program to the user.

// 2. Display via cout a prompt for the Celsius // temperature.

// 3. Read the temperature from cin.

// 4. Compute the Fahrenheit temperature from the // Celsius temperature.

// 5. Display via cout the Fahrenheit temperature // and an informative label. }

When learning to program, it is helpful to just start with the algorithm as comments in

main()

The Code

cout << "John Doe CS 104X -- Lab 1\n\n"; cout << "** Convert Celsius temps to Fahrenheit **\n";

cout << "Please enter a temperature in Celsius: ";15



int main(){ // 1. Display via cout information about the // program to the user.

// 2. Display via cout a prompt for the Celsius // temperature.

The Code

double celsius; cin >> celsius;

double fahrenheit = 1.8 * celsius + 32;

cout << celsius << " degrees Celsius is " << fahrenheit << " degrees Fahrenheit.\n";

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// 3. Read the temperature from cin.

// 4. Compute the Fahrenheit temperature from the // Celsius temperature.

// 5. Display via cout the Fahrenheit temperature // and an informative label.

}

The Code

It’s wise to echo input data to insure computer read what you intended.

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Comments



int main(){ // 1. Display via cout information about the // program to the user. cout << "John Doe CS 104X -- Lab 1\n\n"; cout << "** Convert Celsius temps to Fahrenheit **\n";

// 2. Display via cout a prompt for the Celsius // temperature. cout << "Please enter a temperature in Celsius: ";

Always begin a program with

opening documentation enclosed in /* and */.



int main(){ // 1. Display via cout information to the user. cout << "John Doe CS 104X -- Lab 0\n\n"; cout << "** Convert Celsius temps to Fahrenheit **\n";


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LibrariesThis loads the C++ library that we need.

Lab & Proj. 1: #include <cmath>

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int main(){ // 1. Display via cout information about the // program to the user. cout << "John Doe CS 104X -- Lab 1\n\n"; cout << "** Convert Celsius temps to Fahrenheit **\n";


Each step of the

algorithm is implemented

by one or more C++

program statementsinside main() function.

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// 3. Read the temperature from cin. double celsius; cin >> celsius;

// 4. Compute the Fahrenheit temperature from the // Celsius temperature. double fahrenheit = 1.8 * celsius + 32;

// 5. Display via cout the Fahrenheit temperature // and an informative label. cout << celsius << " degrees Celsius is " << fahrenheit << " degrees Fahrenheit.\n";}

Always a goodidea to

echoinput data

Note spacing, indentation, & alignment to make program “look nice” and easier to read.

This will be one criterion used in grading.

Each step of the

algorithm is implemented

by one or more C++

program statementsinside main() function.

TestingTestingRun your program using sample data (whose correctness is easy to check):

John Doe CS 104X -- Lab 1

** Convert Celsius temps to Fahrenheit **Please enter the temperature in Celsius: 00 degrees Celsius is 32 degrees Fahrenheit.

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** Convert Celsius temps to Fahrenheit **Please enter the temperature in Celsius: 100100 degrees Celsius is 212 degrees Fahrenheit.

When you are convinced that the program is correct, run it with the required data values.


** Convert Celsius temps to Fahrenheit **Please enter the temperature in Celsius: -17.78-17.78 degrees Celsius is -0.004 degrees Fahrenheit.

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For a programming assignment: Lose a few points or may be lucky and the grader doesn’t catch it.

For a real-world problem: Much more may be at stake: money, jobs, and even lives.

Why Testing is Important:

• September,1999: Mars Climate Orbiter

• June, 1996: Ariane 5 rocket

• March,1991: DSC Communications

• February 25, 1991(Gulf War): Patriot missileTesting is never finished; it is only stopped.

Testing can only show the presence of errors, not their absence.

SeeOther Course Information

(CS 104 page):• Importance of

Program Testing — Horror Stories

MaintenanceMaintenance

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• Large % of computer center budgets

• Large % of programmer's time

• Largest % of software development cost

Why?

Poor structure, poor documentation, poor style

less likely to catch bugs before release

fixing of bugs difficult and time-consuming

impede implementation of enhancements

SeeOther Course Information

(CS 104 page):• Time Spent on

Program Maintenance

Programming and Problem Solving — Software Engineering

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