#include <iostream>
#include <string>

void mod (char* data) {
        data[0] = 'c';
}

int main () {
        const std::string str {"8:0.0"};
        std::string dn {str};

        mod (const_cast<char*> (dn.data ()));

        std::cout << "dn = " << dn << "\n";
        std::cout << "str = " << str << "\n";

        return 0;
}