How does a pointer declared with const keyword considered as a pointer to a constant ?

Question

#include<stdio.h>
int main()
{
    int x=3;
    int const *ptr =&x;
    printf("%d",++x);
    printf("\n %d",++*ptr);
    return 0;
}

 

I am unable to get that when x is a variable not a constant then how come the error is that the since ptr is a pointer to a constant hence we cannot change its value, although ++x works fine, whats the logic behind this ?

Answer 1

Type of ptr is pointer to const int, hence it is an error for compiler if we try to change the value it is pointing to.

Answer 2

We must value the type of any data type.

$x$ is an integer and hence we can always modify it.

$ptr$ is a pointer to a constant integer and hence we are not supposed to modify the pointed to value of $ptr$. This is particularly useful when passing a pointer to a function and we want to ensure no modification to the pointed value happens.

Comments

Sir just one confusion that why are we saying that ptr is a pointer to a constant when actually ptr is holding the address of a variable ?

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C language is statically typed- all variables always have the declared type in C.