how to copy char * into a string and vice-versa

Converting a char* to a std::string:

char* c = "Hello, world";
std::string s(c);

Converting a std::string to a char*:

std::string s = "Hello, world";
char* c = new char[s.length() + 1];
strcpy(c, s.c_str());

// and then later on, when you are done with the `char*`:
delete[] c;

I prefer to use a std::vector<char> instead of an actual char*; then you don’t have to manage your own memory:

std::string s = "Hello, world";
std::vector<char> v(s.begin(), s.end());
v.push_back('\0'); // Make sure we are null-terminated
char* c = &v[0];