static arrays index

int x[10];
x[11] = 3;

static multidimensional arrays index

int y[10][10][10];
y[11][-1][10] = 3;

arrays inside structs index

int test.b[-2][3] = 7;
y[11][-1][10] = 3;

null pointers

int test.b[-2][3] = 7;
p = NULL;
*p = 1;