const の指定の仕方とコンパイルエラーについて

レビューで指摘したので、ついでに書いておくことにする。
const を正しく指定しましょうという話。

main.c

char *char1 = "ab";
const char *char2 = "bc";
char *const char3 = "cd";
const char * const char4 = "de";

int main() {
    char1[0] = 'x';
    char1 = "new";

    char2[0] = 'x';
    char2 = "new";

    char3[0] = 'x';
    char3 = "new";

    char4[0] = 'x';    
    char4 = "new";

    return 0;
}

ビルド結果

main.c:12:14: error: read-only variable is not assignable
char2[0] = 'x';
~~~~~~~~ ^
main.c:16:11: error: read-only variable is not assignable
char3 = "new";
~~~~~ ^
main.c:18:14: error: read-only variable is not assignable
char4[0] = 'x';    
~~~~~~~~ ^
main.c:19:11: error: read-only variable is not assignable
char4 = "new";
~~~~~ ^
4 errors generated.