Programming and Problem Solving — Software Engineering (Read Chap. 2) 1.

Programming and Programming and Problem Solving — Problem Solving —

Software Engineering Software Engineering(Read Chap. 2)

1

Problem SolvingProblem Solving

A Temperature-conversion problem:

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

• Implementation (Coding)• Testing, Execution and Debugging• Maintenance

OCD (Object-Centered Design)

2

5 Phases of (Simplified) Software Life Cycle:

• Problem Analysis and Specification• Design

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

1. Describe the behavior of the program.

2. Identify the problem’s objects and make a table of information about them.

3. Identify the problem’s operations and make a table of information about them.

4. Organize the objects and operations into a sequence of steps, called an algorithm, to solve the problem.

3

BehaviorBehavior

A. Describe the desired behavior of the program:

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

4

UsingOCD

Problem ObjectsProblem ObjectsB. Identify the nouns in the behavioral description (other

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

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

These make up the objects in our problem.

5

UsingOCD

cout

cin

Information about ObjectsInformation about ObjectsDetermine a type and a name (if necessary) for each object and whether it is a constant or a variable.

6

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

UsingOCD

C++ Type

?

?

double

?

?

double

?

OperationsOperations

These make up the operations in our problem.

C. Identify the verbs in the behavioral description:

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

7

UsingOCD

Information about Information about OperationsOperations

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

To compute the Fahrenheit temperature, we need to

know/find the Celsius to Fahrenheit conversion formula..

8

OperationPre-defined?

C++ Operato

rLibrary

Display yes << iostreamRead yes >> iostreamCompute the Fahrenheit temperature

?? ?? ??

UsingOCD

Celsius-to-FahrenheitCelsius-to-Fahrenheit

Formula for converting Celsius to Fahrenheit:

fahrenheit = 1.8 × celsius + 32

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

9

UsingOCD

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

10

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

UsingOCD

Information about Information about Operations (Revised)Operations (Revised)

11

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

UsingOCD

AlgorithmAlgorithm

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

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.

12

UsingOCD

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++.

13

14

The Code

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

main()

/*

John Doe CS 104X Input: Output:-----------------------------------------------*/

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

int main(){}

/* 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-----------------------------------------------*/


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. }

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";

16

// 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.

17

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 */.





18

LibrariesThis loads the C++ library that we need.

Lab & Proj. 1: #include <cmath>

19





Each step of the

algorithm is implemented

by one or more C++

program statementsinside main() function.

Why no \n ?

20

// 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";}

Each step of the

algorithm is implemented

by one or more C++

program statementsinside main() function.

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

This will be one criterion used in grading.

Always a goodidea to

echoinput data

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.

21


** 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.

22

23

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

24

• 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 (Read Chap. 2) 1.

Documents

Transcript of Programming and Problem Solving — Software Engineering (Read Chap. 2) 1.