String objects represent character strings in Cocoa frameworks.
Representing strings as objects allows you to use strings
wherever you use other objects. It also provides the benefits of
encapsulation, so that string objects can use whatever encoding
and storage is needed for efficiency while simply appearing as
arrays of characters. A string object is implemented as an array
of Unicode characters (in other words, a text string). An
immutable string is a text string that is defined when it is
created and subsequently cannot be changed. To create and manage
an immutable string, use the NSString class. To construct and
manage a string that can be changed after it has been created,
use The objects you create using NSMutableString are referred to
as string objects (or, when no confusion will result, merely as
strings). The term C string refers to the standard C char *
type. A string object presents itself as an array of Unicode
characters. You can determine how many characters it contains
with the length method a