#include <iostream>
#include <fstream>
using namespace std;

int get_int(int default_value);
char name[ 20 ];

int main() {
    char filename[ 81 ];
    int n;
    int age;
    int recsize = sizeof(name) + sizeof(int);
    

    cout << "Enter file name: ";
    cin.getline(filename,  80 );

    // Open file for binary read and write.    

    fstream  fbin(filename, ios::binary | ios::in | ios::out);
    if (!fbin) {
        cout << "Could not open file " << filename;
        return - 1 ;
    }

//  Get record number to write to.

    cout << "Enter file record number: ";
    n = get_int( 0 );

    // Get data from end user.

    cout << "Enter name: ";
    cin.getline(name,  19 );
    cout << "Enter age: ";
    age = get_int( 0 );

    // Write data to the file.
 
    fbin.seekp(n * recsize);
    fbin.write(name,  20 );
    fbin.write(reinterpret_cast<char*>(&age), sizeof(int));
    fbin.close();
    return  0 ;
}

// Get integer function
// Get an integer from keyboard; return default
//  value if user enters 0-length string.
//
int get_int(int default_value) {
    char s[ 81 ];

    cin.getline(s,  80 );
    if (strlen(s) ==  0 )
         return default_value;
    return atoi(s);
}

#include <iostream>
#include <fstream>
using namespace std;

int main() {
    char filename[ 81 ];

    cout << "Enter a file name and press ENTER: ";
    cin.getline(filename,  80 );
    ofstream file_out(filename);
    if (! file_out) {
        cout << "File " << filename << " could not be opened.";
        return - 1 ;
    }
    cout << "File " << filename << " was opened.";
    file_out << "I am Blaxxon," << endl;
    file_out << "the cosmic computer." << endl;
    file_out << "Fear me.";
    file_out.close();
    return  0 ;
}

fstream  fbin(filename, ios::binary | ios::in | ios::out);