#include #include using namespace std; int main() { string str1 = "Hello"; string str2 = "World"; string str3; int len; // copy str1 into str3 str3 = str1; cout << "str3 : " << str3 << endl; // concatenates str1 and str2 str3 = str1 + str2; cout << "str1 + str2 : " << str3 << endl; // total length of str3 after concatenation len = str3.size(); cout << " str3.size() : " << len << endl; return 0; }