BOOKC, this time share about c++ program to find area of circle using functions
Cpp tutorial to calculate area of circle
•  User enter radius or diameter of circle.
•  Program should have two functions one which takes radius as parameter and second takes diameter as parameter.
•  If user enters wrong option then tell users its valid selection and chose again the right option.
This Cpp Tutorial covers the concept of
• if else if statement
• for loop
• function with parameter and return value
Cpp code compiler used: Codeblocks C++ Compiler

`#include <iostream>#define PI 3.14159using namespace std;float AreaOfCircle(float radius);float AreaWithDiameter(float diameter);int main(){    float radius,diameter,circleArea;    char choice='0';    cout<<"\n\t\t\tFind Area Of Circle:"<<endl;    for(;choice!='1'&&choice!='2';)        {         cout<<"\nEnter 1 to Enter Radius OR                 2 to Enter Diameter: ";         cin>>choice;         if(choice!='1'&&choice!='2')         cout<<"\n\t\tEnter a VALID Option ";        }    if(choice=='1')    {    cout <<"\n\t\tEnter Radius To Find Area: ";    cin>>radius;    circleArea=AreaOfCircle(radius);    }    else if(choice=='2')    {    cout <<"\n\t\tEnter Diameter To Find Area: ";    cin>>diameter;    circleArea=AreaWithDiameter(diameter);    }    cout<<"\n\n\t\tArea of Circle is:->> "<<circleArea<<endl;    return 0;}float AreaOfCircle(float radius){    return (PI*(radius*radius));}float AreaWithDiameter(float diameter){    return (AreaOfCircle(diameter/2));}`

output of program

Program explanation
• Program has two functions one for radius and one for diameter both called upon user choice
• Both calculates the radius and diameter according to formula and return result value from where they have called
• A for loop is used to prevent the wrong choice selection it will break only if user enters valid option 1 or 2 else it will continue to ask user to enter valid option
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