Arrays

Arrays/Heap.cpp

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+//there is no way of knowing the size of array in c++;but there is a way cause when you delete this heap memry compiler needs to know the size of array but its comprimising
+
+#include <iostream>
+#include <array>
+
+class Entity
+{
+    public :
+
+      static const int exampleSize = 5;//constexpr will explained later
+      int* example[exampleSize];//suppose we changed it to a heap we first get the Entity memory adress which leads to the array  its a jumping across the memory so [better to switch it to stack]
+
+    std::array<int, 5> another;
+
+      Entity()
+      {
+
+
+         int a[5];
+
+        int count =  sizeof(a) / sizeof(int);//size means bytes ,count means no of elements 
+
+        //example->size();//we cant do like this like some other languages for heap in Entity class
+           for(int i = 0; i < another.size(); i++)
+             example[i] = 2;//constructor which initializes
+
+      }
+};
+
+int main()
+{
+
+    Entity e;
+
+    /*int example[5];
+    for(int i = 0; i < 5; i++)
+    example[i] = 2;*///we moved into the Entity class
+
+
+    //int* another = new int[5];
+    //for(int i = 0; i < 5; i++)
+    //another[i] = 2;
+
+
+    //delete[] another;
+
+
+    std::cin.get();
+}
+//this is based on heap allocated memory with new keyword
+//we  need to manually delete this
+//stack created it will ends when we get out of curly bracket int example[5]
+//heap created more over the stack cause of the life times most probably suppose if we need to return the array inside of our funtion
+
+//in c++ 11 there is called standard array which has inbuilt datastructures  used rather than the normal raw array
+//it includes bounds checking and it keeps tracking size of arrray

Arrays/Log.cpp

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+#include <iostream>
+
+int main()
+{ 
+    int example[5];
+    int* ptr = example;
+
+
+    for (int i = 0; i < 5; i++)
+            //example[i] = 2;//this is a text an offset to this memory of array
+
+
+
+     example[2] = 5;//for index 2 its start at 9th byte we are writting an offset of 8 bytes from a pointer
+    *(ptr + 2) = 6;//we are dereferencing this pointer way of writting and changing value from 5 to 6
+    *(int*)((char*)ptr + 8) = 6;//this is the way of writting in single bit[char] and even in int data type of 4 bytes
+
+
+    std::cin.get();
+}
+
+//arrays are always stored in rows ; each integer of 4 bytes total 20 bytes;
+//array is just a pointer here it is a integer pointer

Arrays/main.cpp

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+//in java we have no modifier = default modifier
+//in c# we have such as internal[these are topics in visibility]
+/*Arrays in C++ are a collection of multiple elements of the same type stored in contiguous memory locations (one after another).[in rows]
+They are one of the most basic and important data structures in C++.*/
+//lua language starts from index 1;c++ is 0 
+//its like having multiple variables in a single variable
+//arrays mostly work with for loops[indexable loops];without it we need to set manually the example array
+
+#include <iostream>
+
+int main()
+{
+    int example[5]; //array type and name mentioned its contain 5 integers
+    example[0] = 2;
+    example[4] = 4;//last index
+
+    example[-1] = 5;
+    example[17] = 21;//we get memory access violation [in debug mode we get errors not in release mode]
+
+
+    std::cout << example[0] << std::endl;//with mentioning index, we get underlying data type
+    std::cout << example << std::endl;//actual array print memory adress cause its a pointer type
+
+
+
+    std::cin.get();
+}

Interfaces/main.cpp

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+/*Pure virtual function in C++ is the key feature that lets you create interfaces (or abstract classes that behave like interfaces).
+What is a Pure Virtual Function?
+A pure virtual function is a virtual function that:
+
+Has = 0 at the end
+Has no implementation in the base class (or sometimes just a dummy one)
+Forces every derived (child) class to provide its own implementation
+we cant instantiate the interface class [only sub classes we can and have to]
+Interfaces are just classes in c++ with unimplemented methods acting as template of source unlike other languages as java or c#*/
+
+
+#include <iostream>
+#include <string>
+
+  class Printable
+
+    {
+  public :
+     virtual std::string GetClassName() = 0;//now every class have to contain GetClassName function to implement
+
+    };
+
+      class Entity : public Printable//made a sub class
+    {
+        public :
+          virtual std::string GetName() { return "Entity"; }//by removing body and equating to 0 makes a pure virtal funtion
+          std::string GetClassName() override { return "Entity"; } 
+
+        };
+
+    class Player : public Entity //no need of printable 
+    {
+        private :
+          std::string m_Name;
+      public :
+          Player(const std::string& name)
+               : m_Name(name) {}
+
+               std::string GetName() override { return m_Name; }
+               std::string GetClassName() override { return "Player"; } 
+    };
+
+    void PrintName(Entity* entity)
+    {
+          std::cout << entity->GetName() << std::endl;
+    }
+
+    class A : public Printable 
+    {
+       public :
+           std::string GetClassName() override {return "A"; }
+
+    };
+
+
+    void Print(Printable* obj)//this is for printing names of class and type which has GetClassName funtion and make Printable a pointer 
+{
+    std::cout << obj->GetClassName() << std::endl;
+}
+int main()
+{
+
+    Entity* e = new Entity();//cant instantiate the Entity class if it is pure virtual funtion and we need to give a sub class where the funtion is implemented eg Player("")
+   // PrintName(e);
+
+
+    Player* p = new Player("Suhas");
+    //PrintName(p);
+
+    Print(e);
+    Print(p);
+    Print(new A());//it is a memory leak
+
+
+
+    std::cin.get();
+}
+    //we can only instantiate the class if it actually has all those pure virtual functions implemented[all funtions implemented]

Virtual functions/Log.cpp

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+#include <iostream>
+#include <string>
+
+    class  Entity
+    {
+        public :
+          virtual std::string GetName() { return "Entity"; }//getName is going to return string
+
+    };
+
+    class Player : public Entity
+    {
+        private :
+          std::string m_Name;//stores a name
+      public :
+          Player(const std::string& name)//constructor allows to specify a name
+               : m_Name(name) {}
+
+               std::string GetName() override { return m_Name; }//Mark the overriden function with keyword override and this helps the funtion came from the base class
+    };
+
+    void PrintName(Entity* entity)
+    {
+          std::cout << entity->GetName() << std::endl;
+    }
+
+
+int main()
+{
+
+    Entity* e = new Entity();
+    PrintName(e);
+    //std::cout << e->GetName() <<std::endl;
+
+    Player* p = new Player("Suhas");
+    PrintName(p);
+
+    //std::cout << p->GetName() << std::endl;
+
+
+    //Entity* entity = p;//p is pointer to a player type but this is a instance in the player class
+    //std::cout << entity->GetName();//we expect player to be printed
+
+    std::cin.get();
+}
+
+//v table contain a mapping for all the virtual functions in our base class so we can map it to correct overwritten function at runtime 
+//if i want to override a funtion you need to mark the base funtion in the base class as virtual
+//virtual funtions need extra memory to store v table to dispatch to the right funtion includes member pointer in the base class
+//and if we call virtual funtion we have to go through table to see which matches [additional performace penalty] ]

Virtual functions/main.cpp

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+//binding means which functions to call
+//if not virtual it is static binding : The compiler decides at compile time which function to call, based only on the type of the pointer/reference, not the actual object it points to.
+//if it is virtual it is dynamic or runtime binding means the decision of which function to call happens at runtime, based on the actual type of the object.
+//Made possible by virtual functions and the hidden vtable mechanism
+
+//virtual functions allows up to ovverride the methods in the sub classes
+//if parent class has some virtual function then sub class can ovverride it to change the method
+
+#include <iostream>
+#include <string>
+
+    class  Entity
+    {
+        public :
+           std::string GetName() { return "Entity"; }//getName is going to return string
+
+    };
+
+    class Player : public Entity
+    {
+        private :
+          std::string m_Name;//stores a name
+      public :
+          Player(const std::string& name)//constructor allows to specify a name
+               : m_Name(name) {}
+
+               std::string GetName() { return m_Name; }//return the name member
+    };
+
+
+int main()
+{
+
+    Entity* e = new Entity();
+    std::cout << e->GetName() <<std::endl;//created a entity and try to print the getname
+
+    Player* p = new Player("Suhas");
+    std::cout << p->GetName() << std::endl;
+//no need to bothering of objects as program terminates it anyway
+
+    std::cin.get();
+}
+
+//everything goes bad whenever i start introduce polymorphism
+//referring player like its not entity

Visibility/Log.cpp

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+#include <iostream>
+#include <string>
+
+class Entity
+{
+        protected :
+             int X, Y;
+
+
+         void Print(){}    
+
+
+public :
+     Entity()
+     {
+        X = 0;
+        Print();
+     }
+
+};
+
+class Player : public Entity//Player is a subclass of Entity
+{
+   public :
+       Player()
+       {
+        X = 2; 
+        Print();
+       }
+};
+
+int main()
+{
+     Entity e;
+     e.X = 2;
+    e.Print();//its completly different funtion and is outside of class and not even part of sub class
+
+    std::cin.get();
+}
+
+//protected means parent and sub classes along can acccess the symbols
+//public means we know everything can access the subjects ina class

Visibility/main.cpp

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+/*Visibility in C++ refers to access specifiers — they control who can see and use (access) the members (variables, functions, etc.) of a class.
+In simple words:
+Visibility decides which parts of your class are public, private, or protected — i.e., who is allowed to touch them.*/
+//classes are generally private and structs are generally public
+//this visibility has no affect on performance or running or the program and generation of code [not related with CPU]
+//there are even called friends which can access the private
+
+#include <iostream>
+#include <string>
+
+class Entity
+{
+        private :
+             int X, Y;
+
+
+         void Print(){}    
+
+
+public :
+     Entity()
+     {
+        X = 0;//constructor
+        Print();
+     }
+
+};
+
+class Player : public Entity//sub class of Entity
+{
+   public :
+       Player()
+       {
+        X = 2;// Even this constructor cant access the data cause it is private
+        Print();
+       }
+};
+
+int main()
+{
+     Entity e;
+     e.X = 2;// we cant access the subjects from a priavte class
+    e.Print();
+
+    std::cin.get();
+}
+
+//protected is more visible than Private and less visible than public
+//we keep classes public and private according to goal of not breaking the code [such as UIs]USER INTERFACE