C++ ifstream read() Read by data size

#include <fstream>
#include <iostream>
using namespace std;
#include <process.h>   //for exit()
const int MAX = 1000;
int buff[MAX];/*from  w  w w .j  ava 2s . co  m*/
int main()
{
   for(int j=0; j<MAX; j++)            //fill buffer with data
      buff[j] = j;
   ofstream os;                        //create output stream
   //open it
   os.open("a:edata.dat", ios::trunc | ios::binary);
   if(!os)
      { cerr << "Could not open output file\n"; exit(1); }
   cout << "Writing...\n";             //write buffer to it
   os.write( reinterpret_cast<char*>(buff), MAX*sizeof(int) );
   if(!os)
      { cerr << "Could not write to file\n"; exit(1); }
   os.close();                         //must close it
   for(j=0; j<MAX; j++)                //clear buffer
      buff[j] = 0;
   ifstream is;                        //create input stream
      is.open("a:edata.dat", ios::binary);
   if(!is)
   {
      cerr << "Could not open input file\n"; exit(1);
   }
   cout << "Reading...\n";             //read file
   is.read( reinterpret_cast<char*>(buff), MAX*sizeof(int) );
   if(!is)
   {
      cerr << "Could not read from file\n"; exit(1);
   }
   for(j=0; j<MAX; j++){
      if( buff[j] != j )
      {
         cerr << "\nData is incorrect\n";
         exit(1);
      }
   }
   cout << "Data is correct\n";
   return 0;
}