Introduction to Programming with C++, Y. Daniel Liang
Output
Variable Name     Value in Memory
radius
area
  1  #include <iostream>
  2  using namespace std;
  3  
  4  int main()
  5  {
  6    // Step 1: Read in radius
  7    double radius;
  8    cout << "Enter a radius: ";
  9    cin >> radius;
 10  
 11    // Step 2: Compute area
 12    double area = radius * radius * 3.14159;
 13  
 14    // Step 3: Display the area
 15    cout << "The area is " << area << endl;
 16  
 17    return 0;
 18  }