add intro

CPlusPlus/intro/ClassA.cpp

@@ -0,0 +1,23 @@
+#include "ClassA.h"
+
+ClassA::ClassA() : _pNumber(new int(0))
+{
+}
+
+ClassA::ClassA(const ClassA& other)
+{
+	// shallow copy
+	//_pNumber = other._pNumber;
+
+	// deep copy
+	_pNumber = new int(*other._pNumber);
+}
+
+ClassA::~ClassA()
+{
+	if (_pNumber != nullptr)
+	{
+		delete _pNumber;
+		_pNumber = nullptr;
+	}
+}