This is about const keyword in various situations [pointers and refernces ]

const -- types/Log.cpp

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+#include <iostream>
+#include <string>
+
+class Entity
+{
+    private :
+           int m_X, m_Y;
+           mutable int var;
+    public :
+          //const int* const GetX() const //[means cant change the content and cant reassign pointer also cant change member variables of the class through methods] 
+          int GetX() const
+          {
+
+            var = 2;//suppose it needa to modify keep mutable in front of the variable
+            return m_X;     
+          }      
+
+          int GetX()
+          {
+            return m_X;
+          }
+
+          /*keeping const after method in class means 
+              this method cannot modify actual class and its 
+                 belonged variables makes just a
+                  read only method*/
+
+       void SetX(int x)// const makes no sense its setting
+       {
+            m_X = x;  
+       }         
+
+};
+
+   void PrintEntity(const Entity& e)//pass it by conast refernece to avoid copying [just a read only memory]
+   {
+       /*  e = nullptr; 
+         e = Entity(); 
+
+               its not like pointers
+               reassigning this object means changing its own
+               no separation between pointer and contents of the pointer 
+               cause  you are the contents in ref
+               you are the entity though you are a ref
+               and GetX funtion need to be const otherwise it violates const Entity */
+
+        std::cout << e.GetX() << std::endl;
+
+   }
+
+
+   int main()
+   {
+
+    Entity e;
+     const int MAX_AGE = 90;
+
+     const int* const a = new int;
+
+     *a = 2;
+     a = (int*)&MAX_AGE;
+     a = nullptr;
+
+
+     std::cout << *a << std::endl;
+
+     std::cin.get();
+
+
+
+   }
+
+
+//int* m_X, *m_Y //its like both considering pointers

const -- types/main.cpp

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+#include <iostream>
+#include <string>
+
+int main()
+{
+      const int MAX_AGE = 5;//this integer is a constant you cannot change it!
+
+      int* a = new int; //created on heap tO acquire a pointer
+
+      *a = 2;
+      a = (int*)&MAX_AGE;
+
+      int const* a = new int;//contents cant be changed '*a'
+      const int* a = new int;//same as the above
+
+      int*const a = new int;//cant reassign the pointer 'a'
+      const int*const a = new int;//contents and assigning of pointer cant be changed
+
+
+
+            /*dereferencing and equating to 2 [contents]
+            reassigning pointer to some other memory adress*/
+
+      std::cout << *a << std::endl;//reading 'a' is fine
+
+
+
+    std::cin.get();
+}