How do i input number?

Question

I tried to run the programme but output always 0 how do i input number here is the programme

#include <iostream>
using namespace std;

int main() {
float r, area;
printf("enter the value of r");
scanf("%f",&r);
area = 3.1416*r*r;
printf("%.2f",area);
}

Answer 1

cout << "enter the value of r";
cin >> r;

Answer 2

Include stdio.h library to the programme instead of iostream . Printf and scanf functions are available in stdio library not in iostream. For inputs and outputs there is cin and cout as above answers said.