why i can't compile this in visual c++ 6

[jianmin jin]

#include <cstring>

class Text
{
public:
void bad( const string &parm ) const;
private:
char *_text;
};
void Text::bad( const string &parm ) const
{
_text = parm.c_str();
for( int ix = 0; ix < parm.size(); ++ix )
_text[ix] = parm[ix];
}
int main( int argc, char **argv)
{
return 0;
}