C++ :: Float / Double To String Conversion

I want a code that can convert floating/double value into string/char array(char arr[]) and also it can be run on Boreland C++ 5.02

Here I've a code but it doesn't show all the numbers. Instead, it's showing in exponential form which I don't want!!

int main() {
char* str = new char[30];
float flt = 2.4567F;
sprintf(str, "%.4g", flt );
cout<<str<<endl; //Exponential form even after 6 digits without decimal
return 0;
}