C++ Numbers and Strings
Adding Numbers and Strings
WARNING!
C++ uses the + operator for both addition and 
 concatenation.
Numbers are added. Strings are concatenated.
If you add two numbers, the result will be a number:
If you add two strings, the result will be a string concatenation:
Example
  string x = "10";
  string y = "20";
  string z = x + y;   // z will be 1020 (a string)
Try it Yourself »
If you try to add a number to a string, an error occurs:
Example
  string x = "10";
  int y = 20;
  string z = x + y;
