Revisit Simple File I/O Example

//Reads three numbers from the file infile.dat, sums the numbers,

//and writes the sum to the file outfile.dat.

#include <fstream>

#include <iostream>

#include <cstdlib>

int main( )

{

using namespace std;

ifstream in_stream;

ofstream out_stream;

in_stream.open("infile.dat");

if (in_stream.fail( ))

{

cout << "Input file opening failed.\n";

exit(1);

}

out_stream.open("outfile.dat");

if (out_stream.fail( ))

{

cout << "Output file opening failed.\n";

exit(1);

}

int first, second, third;

in_stream >> first >> second >> third;

out_stream << "The sum of the first 3\n"

<< "numbers in infile.dat\n"

<< "is " << (first + second + third)

<< endl;

in_stream.close( );

out_stream.close( );

return 0;

}

The sum of the first 3

numbers in infile.dat

is 6

infile.dat

outfile.dat

Note that there is no output to the screen

and no input from the keyboard