C++ Class Inheritance using English Measures

#include <iostream>
using namespace std;
enum posneg { pos, neg };         //for sign in DistSign
class Measure/*from   ww w.jav a 2s .  c om*/
{
   protected:                     //NOTE: can't be private
   int feet;
   float inches;
   public:                        //no-arg constructor
   Measure() : feet(0), inches(0.0)
   {  }                     //2-arg constructor)
   Measure(int ft, float in) : feet(ft), inches(in)
   {  }
   void getdist()              //get length from user
   {
      cout << "\nEnter feet: ";  cin >> feet;
      cout << "Enter inches: ";  cin >> inches;
   }
   void showdist() const
   { cout << feet << "\'-" << inches << '\"'; }
};
class DistSign : public Measure  //adds sign to Measure
{
   private:
   posneg sign;                //sign is pos or neg
   public:
   //no-arg constructor
   DistSign() : Measure()     //call base constructor
   { sign = pos; }          //set the sign to +
   //2- or 3-arg constructor
   DistSign(int ft, float in, posneg sg=pos) :
   Measure(ft, in)    //call base constructor
   { sign = sg; }           //set the sign
   void getdist()              //get length from user
   {
      Measure::getdist();     //call base getdist()
      char ch;                 //get sign from user
      cout << "Enter sign (+ or -): ";  cin >> ch;
      sign = (ch=='+') ? pos : neg;
   }
   void showdist() const
   {
      cout << ( (sign==pos) ? "(+)" : "(-)" );  //show sign
      Measure::showdist();                     //ft and in
   }
};
int main()
{
   DistSign alpha;                  //no-arg constructor
   alpha.getdist();                 //get alpha from user
   DistSign beta(11, 6.25);         //2-arg constructor
   DistSign gamma(100, 5.5, neg);   //3-arg constructor
   //display all distances
   cout << "\nalpha = ";  alpha.showdist();
   cout << "\nbeta = ";  beta.showdist();
   cout << "\ngamma = ";  gamma.showdist();
   cout << endl;
   return 0;
}