Unresolved external symbol

Hi

I'm new to C++ programming (although I have programmed in other languages) and am just trying to teach myself how to do basic classes. I have some very simple code which asks users for input on their favourite and worst CDs and stores these in two objects of class CD (which I've created). Now I want to add some extra functions to my main program so have declared the favourite and worst CDs as global variables but when I do, I'm getting the following error....

CDClassTest.obj : error LNK2001: unresolved external symbol "public: __thiscall CD::CD(void)" (??0CD@@QAE@XZ)
Debug/ClassExperiments.exe : fatal error LNK1120: 1 unresolved externals

My code is as below....


#include <iostream>
#include <string>
#include "CD.H"

using namespace std;

CD myFavouriteCD;  //global declarations of myFavouriteCD and myWorstCD so that other functions can use them
CD myWorstCD;

string getNameOfArtist()
{
      string inputArtist;
      cout<<"\nPlease enter name of artist: ";
      getline(cin, inputArtist);
      return inputArtist;
}

string getNameOfAlbum()
{
      string inputAlbum;
      cout<<"\nPlease enter title of album: ";
      getline(cin, inputAlbum);
      return inputAlbum;
}

int getNoOfSongs()
{
      int inputNoOfTracks;
      cout<<"\nPlease enter number of tracks : ";
      cin>>inputNoOfTracks;
      return inputNoOfTracks;
}

int getYearOfAlbum()
{
      int inputYear;
      cout<<"\nPlease enter year of album : ";
      cin>>inputYear;
      return inputYear;
}

void modifyFavouriteCD()
{
      //need to modify so that it repeats the question until it gets a valid answer
      int fieldToChange;

      cout<<"Which field do you wish to change? Press 1 for artist, 2 for album name, 3 for number of tracks and 4 for year of album : ";
      cin>>fieldToChange;

      switch(fieldToChange)
      {
      case 1:
            myFavouriteCD.setArtist(getNameOfArtist());
            break;
      case 2:
            myFavouriteCD.setTitle(getNameOfAlbum());
            break;
      case 3:
            myFavouriteCD.setNoOfTracks(getNoOfSongs());
            break;
      case 4:
            myFavouriteCD.setYear(getYearOfAlbum());
            break;
      default:
            cout<<"Not a valid choice";
      }
}

void modifyWorstCD()
{
      //need to modify so that it repeats the question until it gets a valid answer
      int fieldToChange;

      cout<<"Which field do you wish to change? Press 1 for artist, 2 for album name, 3 for number of tracks and 4 for year of album : ";
      cin>>fieldToChange;

      switch(fieldToChange)
      {
      case 1:
            myWorstCD.setArtist(getNameOfArtist());
            break;
      case 2:
            myWorstCD.setTitle(getNameOfAlbum());
            break;
      case 3:
            myWorstCD.setNoOfTracks(getNoOfSongs());
            break;
      case 4:
            myWorstCD.setYear(getYearOfAlbum());
            break;
      default:
            cout<<"Not a valid choice";
      }
}

void modify()
{
      //need to modify so that it repeats the question until it gets a valid answer
      int modifyChoice =0;
      
      cout<<"Which CD do you wish to modify? Press 1 for favourite or 2 for worst : ";
      cin>>modifyChoice;

      switch(modifyChoice)
      {
      case 1:
            modifyFavouriteCD();
            break;
      case 2:
            modifyWorstCD();
            break;
      default:
            cout<<"Not a valid choice";
      }
}

void main()
{
      //get input for first class
      cout<<"Favourite album \n";
      cout<<"=============== \n \n";

      //feed first class values
      myFavouriteCD.setArtist(getNameOfArtist());
      myFavouriteCD.setTitle(getNameOfAlbum());
      myFavouriteCD.setNoOfTracks(getNoOfSongs());
      myFavouriteCD.setYear(getYearOfAlbum());
      
      cin.ignore(); //need to find out why we need this one!!!

      //get input for second class
      cout<<"\n \nWorst album \n";
      cout<<"=========== \n \n";

      //feed second class values
      myWorstCD.setArtist(getNameOfArtist());
      myWorstCD.setTitle(getNameOfAlbum());
      myWorstCD.setNoOfTracks(getNoOfSongs());
      myWorstCD.setYear(getYearOfAlbum());
      

      //print out values of first class
      cout<<"\n \n Favourite album";

      cout<<"\n Artist : "<<myFavouriteCD.getArtist();
      cout<<"\n Title : "<<myFavouriteCD.getTitle();
      cout<<"\n Number of tracks : "<<myFavouriteCD.getNoOfTracks();
      cout<<"\n Year : "<<myFavouriteCD.getYear();

      //print out values of second class
      cout<<"\n \n Worst album";

      cout<<"\n Artist : "<<myWorstCD.getArtist();
      cout<<"\n Title : "<<myWorstCD.getTitle();
      cout<<"\n Number of tracks : "<<myWorstCD.getNoOfTracks();
      cout<<"\n Year : "<<myWorstCD.getYear()<<"\n";

      char modifyChoice;
      
      cout<<"\n Do you wish to modify any of the details? (Y/N) : ";
      cin>>modifyChoice;

      if (modifyChoice == 'Y' || modifyChoice =='y')
      {
            modify();
      }
}



Do I need to add a class definition to this file and if so, how and where does it goes?

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