Why is not there any error?

Question

I defined a Constant pointer to constant Data.

int x = 5;
int y;

const int * const ptrX = &x ;

*ptrX = 8;
// I expected a error and it was accoured.

ptrX = &y;
// I expected a error and it was accoured.

x = 7;
// I expected a error buy it was OK!!!

*ptrX is point to x variable and i think it's as alias for x. So why you can change x, while *ptrX is const value????

Answer 1

The reason why there is no error is that ptrX is a constant pointer to a constant variable, but x is a normal variable.

A constant pointer to a constant variable cannot change the address it is assigned with, nor can it alter the data at the specified address.

But this does not convert the variable x to a constant. x still remains a normal variable, and can modify the data at the address it is allocated at.