Binary File

Write numbers to a binary file and read them back

#include <iostream>#include <fstream>using namespace std;int main(void){   float fnum[4] = {11.22, -33.44, 55.66, 77.88};   int i;   ofstream out("numbers.asc", ios::out | ios::binary);   if(!out){      cout << "Cannot open file.";      exit (1);   }   out.write((char *) &fnum, sizeof(fnum));   out.close();   for (i=0; i<4; i++)      fnum[i] = 0.0;   ifstream in("numbers.asc", ios::in | ios::binary);   if(!in) {      cout << "Cannot open file.";      exit (1);   }   in.read((char *) &fnum, sizeof(fnum));   cout << in.gcount() << " bytes read." << endl;   for (i=0; i<4; i++)      cout << fnum[i] << " ";   in.close();}      

reading a complete binary file

#include <iostream>#include <fstream>using namespace std;ifstream::pos_type size;char * memblock;int main () {  ifstream file ("example.txt", ios::in|ios::binary|ios::ate);  if (file.is_open()){    size = file.tellg();    memblock = new char [size];    file.seekg (0, ios::beg);    file.read (memblock, size);    file.close();    cout << "the complete file content is in memory";    delete[] memblock;  }else     cout << "Unable to open file";  return 0;}      

Binary Files

#include <iostream>using namespace std;  #include <fstream>int main () { long start,end; ifstream myfile ("test.txt", ios::in|ios::binary); start = myfile.tellg(); myfile.seekg (0, ios::end); end = myfile.tellg(); myfile.close(); cout << "size of " << "test.txt"; cout << " is " << (end-start) << " bytes.\n"; return 0;}

seeks particular person in file

#include <fstream>  #include <iostream>    using namespace std;    class person        {       protected:          char name[80];        int age;           public:          void getData(){             cout << "\n   Enter name: "; cin >> name;             cout << "   Enter age: "; cin >> age;          }          void showData(void){             cout << "\n   Name: " << name;             cout << "\n   Age: " << age;          }    };    int main(){       person pers;     ifstream infile;     infile.open("GROUP.DAT", ios::in | ios::binary);         infile.seekg(0, ios::end);          int endposition = infile.tellg();             int n = endposition / sizeof(person);         cout << "\nThere are " << n << " persons in file";           cout << "\nEnter person number: ";       cin >> n;       int position = (n-1) * sizeof(person);       infile.seekg(position);                                                 infile.read( reinterpret_cast<char*>(&pers), sizeof(pers) );       pers.showData();                    cout << endl;       return 0;       }  

binary input and output with integers

#include <fstream>            #include <iostream>  using namespace std;  const int MAX = 100;          int buff[MAX];                  int main(){     for(int j=0; j<MAX; j++)         buff[j] = j;                                               ofstream os("edata.dat", ios::binary);                                   os.write( reinterpret_cast<char*>(buff), MAX*sizeof(int) );     os.close();                     for(int j=0; j<MAX; j++)             buff[j] = 0;                                   ifstream is("edata.dat", ios::binary);     is.read( reinterpret_cast<char*>(buff), MAX*sizeof(int) );     for(int j=0; j<MAX; j++){            if( buff[j] != j ){          cerr << "Data is incorrect\n"; return 1;      }   }        cout << "Data is correct\n";     return 0;  }