title: no default constructor exists for class in C++
body: <p>I have created a constructor, but why there is still have an error &quot;no default constructor exists for class&quot;?
  I have searched for the answer to the question, but I am still not clear about this error. Can someone help me?</p>
  <pre><code>pragma once
  #include&lt;string&gt;
  using namespace std;
  class Date
  {
  private:
      int month;
      int day;
      int year;
  public:
      Date(int newmonth, int newday, int newyear)
      {
          month = newmonth;
          day = newday;
          year = newyear;
      }
  };
  class Student
  {
  private:
      string name;
      Date birthDay;
      int score;
  public:
      Student(string newname, Date newbirthDay, int score)
      {
  
      }
  };
  </code></pre>