Answer by Misaal D'souza for What's the difference between passing by reference vs. passing by value?

1. Pass By Value / Call By Value

   void printvalue(int x)    {       x = x + 1 ;       cout << x ;  // 6   }   int x = 5;   printvalue(x);   cout << x;    // 5

In call by value, when you pass a value to printvalue(x) i.e. the argument which is 5, it is copied to void printvalue(int x). Now, we have two different values 5 and the copied value 5 and these two values are stored in different memory locations. So if you make any change inside void printvalue(int x) it won't reflect back to the argument.

2. Pass By Reference/ Call By Reference

   void printvalue(int &x)    {      x = x + 1 ;      cout << x ; // 6   }   int x = 5;   printvalue(x);   cout << x;   // 6

In call by reference, there's only one difference. We use & i.e. the address operator. By doing
void printvalue(int &x) we are referring to the address of x which tells us that it both refers to the same location. Hence, any changes made inside the function will reflect outside.

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3. Pass By Pointer/ Call By Address

   void printvalue(int* x)    {      *x = *x + 1 ;      cout << *x ; // 6   }   int x = 5;   printvalue(&x);   cout << x;   // 6

In pass by address, the pointer int* x holds the address passed to it printvalue(&x). Hence, any changes done inside the function will reflect outside.