Modularize the program by adding the following 4 functions. None of them have any parameters. void displayMenu() void findSquareArea() void findCircleArea() void findTriangleArea() To do that you will need to carry out the following steps: Write prototypes for the four functions and place them above main. Write function definitions (consisting of a function header and initially empty body) for the four functions and place them below main. Move the appropriate code out of main and into the body of each function. Move variable definitions in main for variables no longer in main to whatever functions now use those variables. They will be local variables in those functions. For example, findSquareArea will need to define the side variable and findCircleArea will need to define the radius variable. All of the functions that compute areas will now need to define a variable named area. Move the definition for the named constant PI out of main and place it above the main function. In main, replace each block of removed code with a function call to the function now containing that block of code.

It is a C++ program  :

#include <iostream>  // to use input output functions

using namespace std;  //to identify objects like cin cout

//following are the prototypes for the four functions placed above main

void displayMenu();  

void findSquareArea();  

void findCircleArea();

void findTriangleArea();

//definition for constant PI out of main

const float PI = 3.14159;  

int main(){  //start of main function

displayMenu(); //calls displayMenu() method

}

  void displayMenu(){  // to make user selection and calls relevant function to compute area according to the choice of user

int selection=0;  //to choose from 4 options

cout<<"Program to calculate areas of objects:\n" ;  //displays this message at start

do  {  //this loop asks user to enter a choice and this continues to execute and calculate depending on users choice until user enters 4 to exit

cout<<"\n1.Square \n2.Circle \n3.Right Triangle \n4.Quit";

cout<<"\nEnter your choice:";  //prompts user to enter choice

cin>>selection;  //reads the input choice

if(selection==1)  //if user enters 1

{  //computes area of square by calling findSquareArea

findSquareArea();  //function call to the findSquareArea function

}  

else if(selection==2)  //if user enters 2

{  //computes area of circle by calling findCircleArea

findCircleArea();  //function call to the findCircleArea function

}  

else if(selection==3)   //if user enters 3

{  //computes area of triangle by calling findTriangleArea

findTriangleArea();  //function call to the findTriangleArea function

}  

else if(selection==4)   //if user enters 4

{  

cout<<"\nTerminating!!.";  //exits after displaying this message

break;

}

else  // displays the following message if user enters anything other than the given choices

{

cout<<"\nInvalid selection";  //displays this message

}

}

while(1);  

}  

void findSquareArea(){  //function definition. this function has no parameters

float area=0.0;  //variable to store the area of square

float side=0;  //local variable of this method that stores value of side of square

cout<<"\nLength of side: ";  //prompts user to enter length of side

cin>>side;  //reads value of side from user

area=side*side;  //formula to compute area of square and result is assigned to area variable

cout<<"\nArea of Square: "<<area<<endl;   //displays are of the square

}  

void findCircleArea(){  //function definition. this function has no parameters

float area=0.0;  //variable to store the area of square

float radius=0.0;  //local variable of this method that stores value of radius of circle

cout<<"\nRadius of circle: ";  //prompts user to enter radius of circle

cin>>radius;  // reads input value of radius

area=PI*radius*radius;  //formula to compute area of circle

cout<<"\nArea of circle: "<<area<<endl;}  //displays are of the circle

void findTriangleArea(){  //function definition. this function has no parameters

   float area=0.0;  //variable to store the area of triangle

   float base=0.0;  //local variable of this method that stores value of base of triangle

   float height=0.0;  //holds value of height of triangle

cout<<"\nHeight of Triangle: ";  //prompts user to enter height

cin>>height;  //reads input value of height

cout<<"\nBase of Triangle: "; //prompts user to enter base

cin>>base;  //reads input value of base

area=0.5*height*base;  //computes area of triangle and assign the result to area variable

cout<<"\nArea of Triangle: "<<area<<endl;  //displays area of triangle

}

Explanation:

The program is modified as above. The prototypes for the four functions that are named as :

void displayMenu();  to display the Menu of choices and call relevant function to compute area

void findSquareArea();  To compute area of square

void findCircleArea(); To compute area of circle

void findTriangleArea();  To compute area of triangle

Note that these methods have no parameters and their return type is void. These 4 methods prototypes are placed above main() function.

Next the function definitions (consisting of a function header and initially empty body) for the four functions are written and placed below main() For example definition of findTriangleArea() is given below:

void findTriangleArea()

{

}

Next the code in the main is moved to the relevant methods. Then variables selection=0;  is moved to displayMenu method,  radius=0.0 to findCircleArea method , side=0; to findSquareArea float area=0.0;  to each method, float height=0.0;  and float base=0.0; to findTriangleArea method.

The relevant code moved to each method is shown in the above code.

The definition for the named constant PI is moved out of main and placed above the main function. const keyword before datatype of PI variable shows that PI is declared constant and its value is initialized once only to 3.14159.