add pure virtual

add interfaces like classes
add template example

CPlusPlus/intro/main.cpp

@@ -3,6 +3,7 @@
 #include <memory>
 #include "functions.h"
 #include "ClassA.h"
+#include "ClassB.h"
 
 int number = 0;
 
@@ -115,8 +116,42 @@ int main()
 
 	//cout << "sn2 refs: " << sn2.use_count() << endl;
 
-	ClassA classA;
-	ClassA classA2 = classA;
+	//ClassA classA;
+	//ClassA classA2 = classA;
+	//ClassB classB;
+
+	//int number = classA.GetNumber();
+	//cout << number << endl;
+	//classB.GetNumber();
+
+	//IComparable* pComparable = nullptr;
+	//pComparable = new ClassB();
+	////ClassB* pClassB2 = (ClassB*)pComparable; // C-Cast, CAUTION: DANGER!!!
+	//ClassB* pClassB2 = dynamic_cast<ClassB*>(pComparable); // C++ polymorph cast
+	//float f = 1.0f;
+	//int i = static_cast<int>(f); // explicit c++ cast between two static data types
+	////int* pNonsense = reinterpret_cast<int*>(pComparable); // c++ cast like C-Cast
+	//const char csz[13] = "Hello World";
+	//char* sz = const_cast<char*>(csz);
+
+	// What's the difference?
+	//const int* cip;
+	//int const* icp;
+	//int* const ipc;
+	//const int* const cipc;
+	//int const* const icpc;
+	//const int const* const cicpc;
+
+	IComparable* pComparable = nullptr;
+	IComparable* pComparable2 = new ClassA();
+	pComparable = new ClassB();
+	(*pComparable).Compare(pComparable2);
+	pComparable->Compare(pComparable2); // identical to line above, but simpler
+	delete pComparable;
+	pComparable = nullptr;
+	//delete pComparable2;
+	//pComparable2 = nullptr;
+	safeDelete(pComparable2);
 
 	return 0;
 }