Double_t mult(Double_t a, Double_t b = 2) {
// multiply a and b 
   return a*b;
}

Double_t mult() {
// prompt for two numbers and return the product
   Double_t a, b;
   cout << "enter a number:";        // output prompt string
   cin >> a;                         // read input
   cout << "enter a second number:"; // output prompt
   cin >> b;                         // read input
   return a*b;                       // return a*b
}