Why in the code “456”+1, output is “56”

Question:

#include <iostream>
int main()
{
    std::cout << "25"+1;
    return 0;
}
I am getting "5" as output.when I use "5"+1,output is blank;"456"+1 output is "56".confused what is going behind the scenes.


Answer:

The string literal "25" is really a char array of type const char[3] with values {'2', '5', '\0'} (the two characters you see and a null-terminator.) In C and C++, arrays can easily decay to pointers to their first element. This is what happens in this expression:

"25" + 1

where "25" decays to &"25"[0], or a pointer to the first character. Adding 1 to that gives you a pointer to 5.

On top of that, std::ostream, of which std::cout is an instance, prints a const char* (note that char* would also work) by assuming it is a null-terminated string. So in this case, it prints only 5.