Using Stream2.cpp and Numconv.cpp as guidelines, create a program that asks for the radius of a circle and prints the area of that circle. You can just use the ‘*’ operator to square the radius. Do not try to print out the value as octal or hex (these only work with integral types).

#include <iostream>
using namespace std;

int main() {
  // Specifying formats with manipulators:
  cout << "a number in decimal: "
       << dec << 15 << endl;
  cout << "in octal: " << oct << 15 << endl;
  cout << "in hex: " << hex << 15 << endl;
  cout << "a floating-point number: "
       << 3.14159 << endl;
  cout << "non-printing char (escape): "
       << char(27) << endl;
} ///:~


#include <iostream>
using namespace std;

int main() {
  int number;
  cout << "Enter a decimal number: ";
  cin >> number;
  cout << "value in octal = 0" 
       << oct << number << endl;
  cout << "value in hex = 0x" 
       << hex << number << endl;
} ///:~