INTERVIEW QUESTIONS C OPERATORS IN C DETAILS

Question: What is a const pointer?

Answer: The access modifier keyword const is a promise the programmer makes to the compiler that the value of a variable will not be changed after it is initialized. The compiler will enforce that promise as best it can by not enabling the programmer to write code which modifies a variable that has been declared const.

A “const pointer,” or more correctly, a “pointer to const,” is a pointer which points to data that is const
(constant, or unchanging). A pointer to const is declared by putting the word const at the beginning of the pointer declaration. This declares a pointer which points to data that can’t be modified. The pointer itself can be modified. The following example illustrates some legal and illegal uses of a const pointer:

const char *str = “hello”;
char c = *str /* legal */
str++; /* legal */
*str = ‘a’; /* illegal */
str[1] = ‘b’; /* illegal */

The access modifier keyword const is a promise the programmer makes to the compiler that the value of a variable will not be changed after it is initialized. The compiler will enforce that promise as best it can by not enabling the programmer to write code which modifies a variable that has been declared const.

A “const pointer,” or more correctly, a “pointer to const,” is a pointer which points to data that is const
(constant, or unchanging). A pointer to const is declared by putting the word const at the beginning of the pointer declaration. This declares a pointer which points to data that can’t be modified. The pointer itself can be modified. The following example illustrates some legal and illegal uses of a const pointer:

const char *str = “hello”;
char c = *str /* legal */
str++; /* legal */
*str = ‘a’; /* illegal */
str[1] = ‘b’; /* illegal */ Source: CoolInterview.com

const pointer: pointer is a constant which points the address of another variable

we can't change the pointer(or
otherwords can't change the
address, pointer points to)

char c[100]="Hello";
char d[100]="Human";
char *const ptr=c; //ptr points c
ptr=d;/* Illegal*/
ptr[3]='Y'; /* Legal*/

pointer to const: The address pointed by pointer is constand that means we can't change the const location value using pointer

char c[100]="Hello";
char d[100]="Human";
const char *p=c;
p[2]='M'; /* Illegal */
p=d; /* Legal */


VENKATGOPU Source: CoolInterview.com

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