[3.13] gh-117291: Explain usage of null bytes in Array(c_char).value (GH-117292) (GH-150651)

(cherry picked from commit 73d8e9a)

Co-authored-by: Patrick Rauscher <prauscher@prauscher.de>

Author: miss-islington

Doc/library/multiprocessing.rst

@@ -1644,7 +1644,10 @@ inherited by child processes.
    Note that *lock* is a keyword only argument.
 
    Note that an array of :data:`ctypes.c_char` has *value* and *raw*
-   attributes which allow one to use it to store and retrieve strings.
+   attributes which can both be used to store and retrieve byte strings.
+   While *raw* allows interaction with a :class:`bytes` object the full size of
+   the array, reading *value* will terminate after a null byte, like most
+   programming languages handle strings.
 
 
 The :mod:`multiprocessing.sharedctypes` module