The user is going to type in three strings, but I need them
to appear in alphabetical order.

Why doesn't this work?

  void swap(string A, string B)
  { const string origA = A;
    A = B;
    B = origA; }

  void main()
  { cout << "Type three words or I'll break your leg. ";
    string X, Y, Z;
    cin >> X >> Y >> Z;
    cout << "You entered " << X << ", " << Y << ", " << Z << "\n";
    if (X > Y)
      swap(X, Y);
    if (Y > Z)
      swap(Y, Z);
    if (X > Y)
      swap(X, Y);
    cout << "In order they are " << X << ", " << Y << ", " << Z << "\n"; }

I need to redefine swap like this:

  void swap(string & A, string & B)
  { const string origA = A;
    A = B;
    B = origA; }

Just those two little ampersands. They make A and B be REFERENCE PARAMETERS,
which are just aliasses or redirections from the names A and B to the
variables provided when swap was called.

Without ampersands, C++ normally uses VALUE PARAMETERS, which are just
temporary copies of the values provided when swap is called.