#include<stdio.h>
#include<conio.h>
#include<stdlib.h>
 
void main ()
{
    double num;
	num=310.589;
     char buffer [10]; 
 
	sprintf(buffer,"%f",num);
	buffer[7]=NULL;
	printf("using &num=\n");
	printf((char *)&num);
	printf("\nbuffer=\n");
	printf(buffer);
	printf("\nfragment of buffer=\n");
	printf((char *)&buffer[3]);
	scanf("%s",buffer);
	num=atof(buffer);
	num/=2;
	printf("\n%lf",num);
                _getch();
}

num=atof(buffer);

printf((char *)&num);

printf( "%f", num ) ;

#include <string>
#include <iostream>
#include <sstream>
using namespace std ;
 
/*void*/ int main()
{
  double num = 310.589 ;
  /* char buffer [10]; */ string buffer ;
  /* sprintf(buffer,"%f",num); */ 
 { ostringstream stm ; stm << num ; buffer = stm.str() ; }
  // buffer[7] = *NULL;
  /*
  printf("using &num=\n");
  printf((char *)&num);
  printf("\nbuffer=\n");
  printf(buffer);
  printf("\nfragment of buffer=\n");
  printf((char *)&buffer[3]);
  */
  cout << "using &num= " << &num << "\nbuffer= " << buffer
       <<  "\nfragment of buffer= " << &( buffer.c_str()[3] ) << '\n' ;
  /* scanf("%s",buffer); */ cin >> buffer ;
  /* num=atof(buffer); */
  {
    istringstream stm(buffer) ;
    stm >> num ;
    if( !stm ) cerr << "conversion failed\n" ;
  }
  num/=2;
  /* printf("\n%lf",num); */ cout << num << '\n' ;
  /* _getch(); */ char ch ; cin >> ch ;
}

#include <string>
#include <iostream>
#include <sstream>
#include <boost/lexical_cast.hpp>
using namespace std ;
using namespace boost ;
 
int main()
{
  double num = 310.589 ;
  string buffer = lexical_cast<string>(num) ;
  cout << "using &num= " << &num << "\nbuffer= " << buffer
       <<  "\nfragment of buffer= " << &( buffer.c_str()[3] ) << '\n' ;
  cin >> buffer ; 
  try { num = lexical_cast<double>(buffer) ; }
  catch( const bad_lexical_cast& ) { cerr << "cast error\n" ; }
  num/=2;
  cout << num << '\n' ;
  char ch ; cin >> ch ;
}

printf("using &num= %p\n", &num);

 stringstream(buffer)>>num;