c++中反斜杠'\'的问题

Question

#include <iostream>

using namespace std;

int main()
{
    cout << (int)'\1' << endl;
    cout << 1 << endl;

    cout << (int)'\11' << endl;
    cout << 11 << endl;

    return 0;
}

请问，(int)'11'这样输出为什么是9啊？

Answer 1

Escape sequence

There are five types of escape sequences: Simple, Octal, Hexadecimal, Unicode (UTF-8) and Unicode (UTF-16). The escape sequence can be any of the following:

See Strings and Character Literals (C++)