Expalin me about following statements

char * const ptr1="GOOOD";//constant pointer

int const * ptr2=&m; //pointer to a constant

What is difference between them?
I can't get these statements.
Please help me.

Thank you in advanced.

Hi friend,

Look at this below code snippet, it sure help you in understanding the differences :)

void Foo( int * ptr,
          int const * ptrToConst,
          int * const constPtr,
          int const * const constPtrToConst )
{
    *ptr = 0; // OK: modifies the pointee
    ptr = 0; // OK: modifies the pointer

    *ptrToConst = 0; // Error! Cannot modify the pointee
    ptrToConst = 0; // OK: modifies the pointer

    *constPtr = 0; // OK: modifies the pointee
    constPtr = 0; // Error! Cannot modify the pointer

    *constPtrToConst = 0; // Error! Cannot modify the pointee
    constPtrToConst = 0; // Error! Cannot modify the pointer
}

Regards,
S.Manivannan

Constant Pointer: It means that the address that the pointer is pointing to cannnot be changed. Consider this
char str[] = "Hello";
char * const ptr = &str;
In the above two statements first we have created an array of char called str then in the next statement we have created a char pointer ptr which points to str. Since prt is a constant pointer it can only point to str. i.e if we write something like ptr = &str1. the compiler will flag an error because we cannot change the contents of pointer ptr though we can change the contents of string str;

Pointer to Constant: It simply means that the string is constant and the pointer is not constant. Now we can change the contents of pointer but not that of string through the use of pointer.
char str[] = "Hello";
const char * ptr = &str;
char str1[] = "World"
*(ptr+2) = 't' //error constant pointer cannot be used to modify string
ptr = &str1 //ok