1   // Fig. 14.12: Fig14_12.cpp
 2   // Writing to a random-access file.
 3   #include <iostream>
 4   #include <fstream>
 5   #include <cstdlib>
 6   #include "ClientData.h" // ClientData class definition
 7   using namespace std;
 8
 9   int main()
10   {
11      int accountNumber;
12      string lastName;
13      string firstName;
14      double balance;
15
16      fstream outCredit( "credit.dat", ios::in | ios::out | ios::binary );
17
18      // exit program if fstream cannot open file
19      if ( !outCredit )
20      {
21         cerr << "File could not be opened." << endl;
22         exit( EXIT_FAILURE );
23      } // end if
24
25      cout << "Enter account number (1 to 100, 0 to end input) ? ";
26
27      // require user to specify account number
28      ClientData client;
29      cin >> accountNumber;
30
31      // user enters information, which is copied into file
32      while ( accountNumber > 0 && accountNumber <= 100 )
33      {
34         // user enters last name, first name and balance
35         cout << "Enter lastname, firstname, balance ? ";
36         cin >> lastName;
37         cin >> firstName;
38         cin >> balance;
39
40         // set record accountNumber, lastName, firstName and balance values
41         client.setAccountNumber( accountNumber );
42         client.setLastName( lastName );
43         client.setFirstName( firstName );
44         client.setBalance( balance );
45
46         // seek position in file of user-specified record   
47         outCredit.seekp( ( client.getAccountNumber() - 1 ) *
48            sizeof( ClientData ) );                          
49
50         // write user-specified information in file                  
51         outCredit.write( reinterpret_cast< const char * >( &client ),
52            sizeof( ClientData ) );                                   
53
54         // enable user to enter another account
55         cout << "Enter account number ? ";
56         cin >> accountNumber;
57      } // end while
58   } // end main