9B

#define _CRT_SECURE_NO_WARNINGS
#include <iostream>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>

using namespace std;
FILE *fl;
FILE *ft;

struct worker
{
    char surname[50];
    int birthdate;
    int workdate;
} *spisok, rabotnik;
char fname[20];

void vvod();    //Ввести список
void chit();    //Прочитать список
void reze();    //Вывести результат на экран
void rezf();    //Вывести результат в файл
int menu();    //Меню
char * fnam();    //Ввод имени файла


int main()
{
    while (true)
    {
switch (menu())
{
case 1: vvod(); break;
case 2: chit(); break;
case 3: reze(); break;
case 4: rezf(); break;
case 5: return 0;
default: cout << "Choose correct!" << endl;
}
         cout << "Press any key" << endl;
    }
}

int menu()
{
    cout << "Choose: " << endl;
    cout << "1.Vvesti spisok" << endl;
    cout << "2.Chitat' spisok" << endl;
    cout << "3.Rez na ekran" << endl;
    cout << "4.Rez v file" << endl;
    cout << "5.Exit" << endl;
    int x;
    cin >> x;
    return x;
}

char * nnf()
{
    if (strlen(fname))
        return fname;
    cout << "Enter the name of file: " << endl;
    cin >> fname;
    return fname;
}

void vvod()
{
    if ((fl = fopen(nnf(), "ab")) == NULL)
         if ((fl = fopen(nnf() , "wb")) == NULL)
         {
             cout << "File is not created" << endl;
             return;
         }
    int n;
    cout << "Enter amount of workers: ";
    cin >> n;
    spisok = new worker[n];
    for (int i = 0; i < n; i++)
    {
        cout << "Enter the surname of worker:  ";
        cin >> rabotnik.surname;
        cout << "Enter the birthdate of worker: ";
        cin >> rabotnik.birthdate;
        cout << "Enter the date of first work: ";
        cin >> rabotnik.workdate;
        cout << endl;
    }
     fclose(fl);
    }

void chit()
{
         if ((fl = fopen(nnf(), "rb+")) == NULL)
         {
             cout << "File wasn't read" << endl;
         }
         else cout << "File was readed" << endl;

         int n = 0;

         while (fread(&spisok, sizeof(spisok), 1, fl) == 1) //find number of structeres in file
         {
             n++;
         }
         rewind(fl);

         for(int i=0; i<n ; i++)
         {
             fread(&rabotnik, sizeof(spisok), 1, fl);
             cout << "Enter the surname of worker:  " << rabotnik.surname << endl;
             cout << "Enter the birthdate of worker: " << rabotnik.birthdate << endl;
             cout << "Enter the date of first work: " << rabotnik.workdate << endl;
         }
       fclose(fl);
}

void reze()
{
       if ((fl = fopen(nnf(), "rb+")) == NULL)
 {
       cout << "File wasn't read" << endl;
 }
       else cout << "File was readed" << endl;
       rewind(fl);
    int n;
    cout << "Enter amount of workers: ";
    cin >> n;
    spisok = new worker[n];
    for (int i = 0; i < n; i++)
    {
        fread (&spisok, sizeof(spisok), 1, fl);
        if (spisok[i].birthdate < 1980)
    {
        cout << "Worker that is not earlier than 1980: " << spisok[i].surname << endl;
        cout << "His birth date: " << spisok[i].birthdate << endl;
        cout << "His date of first work: " << spisok[i].workdate;
        cout << endl;
    }
       else cout << "> 1980";
    }

    delete[] spisok;
    fclose(fl);
}

void rezf()
{
    char fnamet[20];
    cout << "Enter the name of file: ";
    cin >> fnamet;

    if ((ft = fopen(fnamet, "w")) == NULL)
    {
          cout << "File wasn't read" << endl;
    }
          else cout << "File was readed" << endl;
          rewind(ft);
    if ((fl = fopen(nnf(), "rb+")) == NULL)
    {
          cout << "File wasn't read" << endl;
    }
          else cout << "File was readed" << endl;
          rewind(fl);
    int n;
       cout << "Enter amount of workers: ";
       cin >> n;
       spisok = new worker[n];
       for (int i = 0; i < n; i++)
       {
           fread(&spisok, sizeof(spisok), 1, fl);
           if (spisok[i].birthdate < 1980)
           {
               cout << "Worker that is not earlier than 1980: " << spisok[i].surname << endl;
               cout << "His birth date: " << spisok[i].birthdate << endl;
               cout << "His date of first work: " << spisok[i].workdate;
               cout << endl;
           }
              else cout << "> 1980";
           }
    fclose(ft);
    fclose(fl);
}