Thus, in general a string might contain any character. In particular, a string might contain the contents
of a binary file.
Passing a null pointer as cstr results in undefined behavior.
See Table 13.3 for an overview of which operation uses which kind of arguments. All operators
can handle only objects as single values. Therefore, to assign, compare, or append a part of a string
or C-string, you must use the function that has the corresponding name.