how to understand const and pointer in C++ expression below?

I am reading application code developed in the IBM RSARTE C++ version. Here is a piece of C++ code:

const char * const * av = RTMain::argStrings();

How to understand the left-hand side syntax when there are two const and two *?

>Solution :

const char * const * av = RTMain::argStrings();

is the same as

char const * const * av = RTMain::argStrings();

const applies to what’s left of const.

So, av is a non-const pointer to a const* to const char.

• The returned pointer, av, is non-const and can be changed.
• The pointer av is pointing at is const and can not be changed.
• The char that pointer is pointing at is const and can not be changed.