c - why a pointer can be assigned value? -

i have puzzle here:

int *a=*b; a[1]=3; a[2]=5 

a pointer array , assigned value b. in understanding, a[]should address, why in practice can assign value place pointer (in case a[]) to? explain?

i'm assuming c, or c subset of objective c/c++, since c+, java, php, , other c-like languages don't use pointers.

use code tags , single statement per line.

the statement

int *a = *b; 

creates pointer int. not pointer pointer int, pointer int.

it sets current address in a dereference of b, whatever b is. did not show declaration of b. unless b of type int **, should getting compiler warning.

a not pointer array. pointer int. point single int, or made point array of ints. compiler can't tell difference..

if b of type int **, or pointer pointer int, statement dereferences 1 of pointers , makes point first sub-array inside b.

the code

a[1] = 3; 

assumes pointer array of integers, , since compiler can't range checking, tries index array , save value second int in block of memory points to. if not point block of memory large enough contain @ least 2 integers, statement may crash on modern computer using protected memory, might overwrite memory follows.

as @eds. points out in comment below, known in business

"undefined behavior"

if you're going use c pointer this, burden on make sure points valid memory, , if you're going use pointer if it's array, burden on make sure don't exceed bounds of memory pointed pointer.