Difference between const char*p, char*const p and const char*const p in C

Pointer

In the C programming language, *p represents the value stored in the pointer, and p represents the address of the value, which is called a pointer.

const char* and char const* indicate that the pointer can point to a constant character, and the value of the character pointed to by the pointer cannot be changed. But we can change the value of the pointer because it is not a constant and can point to another constant character.

char* const means that the pointer can point to a character, and the value of the character pointed to by the pointer can be changed. But we cannot change the value of the pointer because it is now a constant and cannot point to another character.

const char* const means that the pointer can point to a constant character, and the value of the character pointed to by the pointer cannot be changed. We also cannot change the value of the pointer because it is now a constant and cannot point to another constant character.

The principle of naming syntax is from right to left.

// constant pointer to constant char
const char * const
// constant pointer to char
char * const
// pointer to constant char
const char *

Example (C)

Uncomment the erroneous code and view the error.

Real-time demonstration

#include <stdio.h>
int main() {
   //Example: char const*
   //Note: char const* is same as const char*
   const char p = &#39;A&#39;;
   // q is a pointer to const char
   char const* q = &p;
   //Invalid asssignment
   // value of p cannot be changed
   // error: assignment of read-only location &#39;*q&#39;
   //*q = &#39;B&#39;;
   const char r = &#39;C&#39;;
   //q can point to another const char
   q = &r;
   printf("%c</p><p>", *q);
   //Example: char* const
   char u = &#39;D&#39;;
   char * const t = &u;
   //You can change the value
   *t = &#39;E&#39;;
   printf("%c", *t);
   // Invalid asssignment
   // t cannot be changed
   // error: assignment of read-only variable &#39;t&#39;
   //t = &r;
   //Example: char const* const
   char const* const s = &p;
   // Invalid asssignment
   // value of s cannot be changed
   // error: assignment of read-only location &#39;*s&#39;
   // *s = &#39;D&#39;;
   // Invalid asssignment
   // s cannot be changed
   // error: assignment of read-only variable &#39;s&#39;
   // s = &r;
   return 0;
}

Output

C
E

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