关于c++ char char*

#include <iostream>

int main()
{
    char* s1 = new char('a');
    char s2 = { 'a' };
    char* s3 = new char[10];
    const char* s4 = "aaa";
    char* s5 = new char[4]{ "aaa" };
    *s5 = 'n';
    char* s6 = const_cast<char*>( "aaa" );
    //*s6 = 'n';
    char s7[3] = {'a','a','a'};
    *s7 = 'n';
}