how to ad mopre char to string in c+= code example

Example 1: c++ char to string

#include <iostream>
using namespace std;

int main()
{
  char c = 'l';
  string str;
  str.push_back(c);
}

Example 2: why convert char* to string c++

char *cStr = "C++";
std::string Str = std::string(cStr);