What is the difference between char * const and const char *?

Question

What\'s the difference between:

char * const 

and

const char *

Answer 1

const * char is invalid C code and is meaningless. Perhaps you meant to ask the difference between a const char * and a char const *, or possibly the difference between a const char * and a char * const?

See also:

• What are const pointers (as opposed to pointers to const objects)?
• Const in C
• Difference between const declarations in C++
• C++ const question
• Why can I change the values of a const char* variable?

Answer 2

char * const and const char *?

1. Pointing to a constant value

const char * p; // value cannot be changed

2. Constant pointer to a value

char * const p; // address cannot be changed

3. Constant pointer to a constant value

const char * const p; // both cannot be changed.

Answer 3

I would like to point out that using int const * (or const int *) isn't about a pointer pointing to a const int variable, but that this variable is const for this specific pointer.

For example:

int var = 10;
int const * _p = &var;

The code above compiles perfectly fine. _p points to a const variable, although var itself isn't constant.

Answer 4

1. const char* x Here X is basically a character pointer which is pointing to a constant value

2. char* const x is refer to character pointer which is constant, but the location it is pointing can be change.

3. const char* const x is combination to 1 and 2, means it is a constant character pointer which is pointing to constant value.

4. const *char x will cause a compiler error. it can not be declared.

5. char const * x is equal to point 1.

the rule of thumb is if const is with var name then the pointer will be constant but the pointing location can be changed , else pointer will point to a constant location and pointer can point to another location but the pointing location content can not be change.

Answer 5

Here is a detailed explanation with code

/*const char * p;
char * const p; 
const char * const p;*/ // these are the three conditions,

// const char *p;const char * const p; pointer value cannot be changed

// char * const p; pointer address cannot be changed

// const char * const p; both cannot be changed.

#include<stdio.h>

/*int main()
{
    const char * p; // value cannot be changed
    char z;
    //*p = 'c'; // this will not work
    p = &z;
    printf(" %c\n",*p);
    return 0;
}*/

/*int main()
{
    char * const p; // address cannot be changed
    char z;
    *p = 'c'; 
    //p = &z;   // this will not work
    printf(" %c\n",*p);
    return 0;
}*/



/*int main()
{
    const char * const p; // both address and value cannot be changed
    char z;
    *p = 'c'; // this will not work
    p = &z; // this will not work
    printf(" %c\n",*p);
    return 0;
}*/

Answer 6

Another thumb rule is to check where const is:

1. before * => value stored is constant
2. after * => pointer itself is constant