Save and read double array in a binary file : ofstream « File Stream « C++ Tutorial

#include <iostream>
#include <fstream>
using namespace std;

int main()
{
  double fnum[4] = {9.5, -3.4, 1.0, 2.1};
  int i;

  ofstream out("numbers", ios::out | ios::binary);
  if(!out) {
    cout << "Cannot open file.";
    return 1;
   }

  out.write((char *) &fnum, sizeof fnum);

  out.close();

  for(i=0; i<4; i++) // clear array
    fnum[i] = 0.0;

  ifstream in("numbers", ios::in | ios::binary);
  in.read((char *) &fnum, sizeof fnum);

  // see how many bytes have been read
  cout << in.gcount() << " bytes read\n";

  for(i=0; i<4; i++) // show values read from file
  cout << fnum[i] << " ";

  in.close();

  return 0;
}

32 bytes read
9.5 -3.4 1 2.1 "

12.10.ofstream
	12.10.1.	Save char array to a file
	12.10.2.	Read char array from a file
	12.10.3.	Writing on a text file
	12.10.4.	Writing numbers to a file
	12.10.5.	ofstream: seek from beginning
	12.10.6.	Save and read double array in a binary file
	12.10.7.	Save and read structure
	12.10.8.	Save chars to a binary file
	12.10.9.	Demonstrate peek(), unget(), and ignore().
	12.10.10.	Create a sequential file.