Terninate called after throwing an instance of 'std: logic_error 'What (): basic_string ::_

Error message:
An incorrect logic of Instantiation causesProgramAbort.
In the what () function, null cannot be used to construct the basic_string object.

Demo of incorrect usage:
======================================
# Include <string>
Using namespace STD;

Void main (void)
{
// String a (null); // incorrect usage
// String B = NULL; // incorrect usage
String A (""); // correct usage
String B = ""; // correct usage
String C; // correct usage

A = "AAA ";
B = "bbbbb ";
C = "CCC ";
Printf ("A = % s \ NB = % s \ NC = % s \ n", A. c_str (), B. c_str (), C. c_str ());

Getchar ();
}