Accessing Elements

Subscripts
char  c  =  s[5];  // get 6th char
s[5]  =  'a';  // set 6th char
Not bounds checked
at() member function
char  c  =  s.at(5);  // get 6th char
s.at(5)  =  'a';  // set 6th char
Bounds checked
s.size()  and  s.length()
Length of string