Functions and Classes in C++

Here is the sample application of Functions and Classes in c++.

Things to note:

1.      Identify the object or class

2.      Identify its properties

3.      Identify its functions: usually they are the following:

a.      Function of each input

b.      Function for calculations and display

4.      Then, define and order them in the program

Click the jump for an example.

Create a program that would ask the user for the radius of a circle and display its area and circumference.

The things to note would be

1.      Object: Circle

2.      Properties: radius, area, circumference & pi(3.1416)

3.      Functions

a.      1 function for input radius

b.      2 functions for calculate and output (radius and circumference)

4.      First input, calculate and then output.

Project: Circle

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#include "stdafx.h"           //include libraries

#include <iostream>

#include <string>

using namespace std;

const double pi = 3.1416; //declared outside since global and constant

class Circle {          //define the class in this format

private:  //declare properties of class in private

 double radius, area, circumference;

public:

 void setRadius(); //func to set Radius. void since it won’t return any

 double calcArea(); //func to return the value of area

 double calcCircumference(); //function to return the circumference

};

int main(){

      Circle c1, c2;//declare two objects of the class Circle, c1 and c2

      c1.setRadius();   //input for radius of c1
      //calculate for area of c1

      cout << "The area of c1 is " << c1.calcArea(); 
      //calculate circumference of c1

      cout << "\nThe circumference if c1 is " << c1.calcCircumference();

      c2.setRadius(); //input for radius of c2
      //calculate for area of c2

      cout << "The area of c2 is " << c2.calcArea();
      //calculate circumference of c1

      cout << "\nThe circumference if c2 is " << c2.calcCircumference();

      system("pause");

      return 0;

}

void Circle::setRadius(){

      cout << "\n\nEnter the radius of the circle: ";

      cin >> radius;

}

double Circle::calcArea(){

      area = pi * radius * radius;

      return area;      //when calling, return the value of area

}

double Circle::calcCircumference(){

      circumference = 2 * pi * radius;

      return circumference;   //when calling, return the circumference

}

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Based on the sample, create the following programs with the use of class and functions:

1.      Project: Triangle

Ask for the base and the height of a triangle, calculate and display its area. (a = ½ bh)

2.      Project: calcAge

Ask the user for his first name, last name, and birthday in days, month and year, then display the age of the user(assuming that today is March 5, 2013).

Test Case1:

Enter first name: Jen

Enter last name: Lerio

Birthday: Day: 13

Month: 1

Year: 2003

            Jen Lerio is 10 years old

Test Case 2:

Enter first name: Jack

Enter last name: Cruz

Birthday: Day: 12

Month: 12

Year: 1993

            Jack Cruz is 19 years old