Linking problem in VC++

hi,
   I have the following class:

   #include <iostream.h>
   #include <string.h>
   #include <stdio.h>
     
   #ifndef STR
   #define STR
     
   class TPString
   {
   private:
   char *buf; // to contain the data
   int len; // length of this buffer
     
   public:
        // Constructors
   TPString();
   TPString(  char *aBuf );
   TPString(  TPString& rhs );
     
   // Destructors
   ~TPString();
     
           // Concatenations
     TPString  operator+(  TPString& rhs );
   friend TPString  operator+ (  char* lhs,  TPString& rhs );
            // Assignments
   TPString& operator=(  TPString& rhs );
   TPString& operator=(  char* rhs );
   };
     
   When I compile and build my main function, I have the following link errors:

   main.obj : error LNK2001: unresolved external symbol "public: __thiscall TPString::~TPString(void)"
   (??1TPString@@QAE@XZ)
   main.obj : error LNK2001: unresolved external symbol "public: __thiscall TPString::TPString(class TPString &)"
   (??0TPString@@QAE@AAV0@@Z)
   main.obj : error LNK2001: unresolved external symbol "public: class TPString & __thiscall
   TPString::operator=(char *)" (??4TPString@@QAEAAV0@PAD@Z)
   main.obj : error LNK2001: unresolved external symbol "public: __thiscall TPString::TPString(void)"
   (??0TPString@@QAE@XZ)
   main.obj : error LNK2001: unresolved external symbol "class ostream & __cdecl operator<<(class ostream
   &,class TPString &)" (??6@YAAAVostream@@AAV0@AAVTPString@@@Z)
   main.obj : error LNK2001: unresolved external symbol "public: class TPString & __thiscall
   TPString::operator=(class TPString &)" (??4TPString@@QAEAAV0@AAV0@@Z)

   Can any expert please advise what happens and how can i solve/prevent the same errors.

   Thanks very much.
   Andrea