/*
 * const char * const
 *      : Nothing about it can be changed
 *
 * const char *     ==      char const *
 *      : that is a pointer [const char]
 *      Why same? const char * A; the char value A points to can't be changed
 *      char const * A; The A pointer
 *
 * char const *
 *      : that is constant pointer to a [char]
 *
 * const int *foo, *bar;
 *      : both foo, bar are [int const *]
 *
 * char * const cp      ==      char const * cp
 *      : the constant variable cp which is the pointer to char.
 *      : cp's value can't be changed.
 *
 */

/*
 * First two const char *p and char const *p both are same i.e. points to constant character
 * (You can change where p points, but you can’t change pointed characters using that pointer).
 */

#include <stdio.h>

int main(int argc, char* argv[])
{
#ifdef  DEFAULT
    // const char and char const is the same.
    const char const * const a; // duplicated!
    const char * const b;   // Nothing about it can be changed.
    const char *c;          // the value c points to can't be changed.
    char const *d;          //
    char * const e;
    char f = 'f';
    char g = 'g';
#endif

    /* b */
#ifdef  B1
    char f = 'f';
    char g = 'g';
    const char * const b = &f;  // b has f's mem addr. after that can't be changed
    printf("%s\n", b);
    b = &g;                     // Error. can't be assigned mem addr at b.
    printf("%s\n", b);
#endif

#ifdef  B2
    char f = 'f';
    char g = 'g';
    const char * const b = &f;  // b has f's mem addr. after that can't be changed
    printf("%s\n", b);
    *b = "ff";                  // Error. can't be changed at the value b points to.
    printf("%s\n", b);
#endif

    /* c */
#ifdef  C1
    char f = 'f';
    char g = 'g';
    const char *c = &f;         // the value c points to can't be changed.
    printf("%s\n", c);
    c = &g;
    printf("%s\n", c);
#endif

#ifdef  C2
    char f = 'f';
    char g = 'g';
    const char *c = &f;         // the value c points to can't be changed.
    printf("%s\n", c);
    *c = "ff";                  //Error. can't be changed at the value c points to.
    printf("%s\n", c);
#endif

    /* d */
#ifdef  D1
    char f = 'f';
    char g = 'g';
    char const *d = &f;          // The same with c variable above.
    printf("%s\n", d);
    d = &g;     //Error
    printf("%s\n", d);
#endif

#ifdef  D2
    char f = 'f';
    char g = 'g';
    char const *d = &f;         // The same with c variable above.
    printf("%s\n", d);
    *d = "ff";                  //Error.
    printf("%s\n", d);
#endif

    /* e */
#ifdef  E1
    char f = 'f';
    char g = 'g';
    char * const e = &f;        // var e can't be assigned another mem addr which is char.
    printf("%s\n", e);
    e = &g;                     //Error.
    printf("%s\n", e);
#endif

#ifdef  E2
    char f = 'f';
    char g = 'g';
    char * const e = &f;         // var e can't be assigned another mem addr which is char.
    printf("%s\n", e);
    *e = 'z';
    printf("%s\n", e);
#endif

    return 0;
}