/*
Create a file and print to a file instead of printing to the screen with the help of fstream directive.
//stream: Flow of characters or other kind of data. 
Flow could be into the program (INPUT STREAM) or out of the program (OUTPUT STREAM).
Input & output sources: Keyboard/ screen, file.
WHAT YOU NEED: create a file input_file.dat and enter three numbers.
*/
#include <cstdlib>
#include<iostream>
#include<fstream>
using namespace std ;
int main()

{ 
 
ifstream in_stream ; // input is being delivered to the program via a C++ construct known as a stream.
ofstream out_stream ; // output via a stream .

in_stream.open("input_file.dat");//read from file //open here means open for input
out_stream.open("output_file.dat");//write to file//open here means open for output
if (in_stream.fail())
{
cout << "FAIL!";
exit(1); //causes the program to end!
}
int  _1st, _2nd,_3rd;

in_stream >> _1st >> _2nd >> _3rd ;
cout<< "the sum of the first 3 \n"
           << "numbers in the input_file.dat \n"
           << "is " << (_1st + _2nd + _3rd)
           << endl;
in_stream.close(); //very important to close the files which were opened.
out_stream.close();


return 0;
}

/*
Task: 
1. Please generate an array of 1000 numbers between 0 and 50 and write the output to a file array.dat.

2. Now use the array.dat file as an input file and group these numbers into even and odd numbers.


*/