Question

The user inputs books which I have to collect in an array.
Could you help me understand why when I enter the second book, the first one is erisen?
I defined BOOK aux globally…

Could you help me understand why I can’t collect

#define   stop __asm nop
#include "book.h"
#include <iostream>
#include <cstdio>

using namespace std;

int counter = 0;
BOOK aux [1];

void print_catalogue()
{

}

void print_book(BOOK aBook)
{
    cout << endl;
    cout <<aBook.Autor<<", "<<aBook.Title<<", "<<aBook.Year<<", "<<aBook.PageCount<<", "<<aBook.Cost<<endl; 
}


void new_book()
{
    BOOK temp;
    system("cls");
    cin.getline (temp.Autor, 20);
    cout <<"ENTERING NEW BOOK: " << endl <<endl;
    cout <<"Input the author: ";
    cin.getline (temp.Autor, 20);
    cout  <<"Input the title: ";
    cin.getline (temp.Title, 50);
    cout  <<"Input the year of publishing: ";
    cin >>  temp.Year;
    cout  <<"Input the number of pages: ";
    cin >>  temp.PageCount;
    cout  <<"Input the cost: ";
    cin >>  temp.Cost;
    cout << endl;   

    counter++;

    BOOK * pn = new BOOK [counter];
    if (counter > 0)
    {
        memcpy(pn, aux, counter * sizeof(BOOK));    
    }
    pn[counter - 1] = temp;

    BOOK * aux = new BOOK[counter];
    memcpy(aux,pn, counter * sizeof(BOOK));

    delete[] pn;

    for (int i = 0; i < counter; i++)
    {
        print_book(aux[i]);
    }   

    system("pause");
    return;
}

void delete_books()
{

}

 void write_catalogue()
 {

 }

 void read_catalogue()
 {

 }

void menu()
{
    char command;
    do
    {       
        system("cls");

        cout << "p - Print the whole catalogue."<< endl;
        cout << "n - Input a new book." << endl;
        cout << "d - Delete existing book(s)." << endl;
        cout << "w - Write the catalogue to a file." << endl;
        cout << "r - Read the catalogue from a file." << endl;
        cout << "Input a new command: ";
        cin >> command;


        cout << endl << endl;
        switch (command) 
        {
            case 'p': print_catalogue(); break;
            case 'n': new_book(); break;
            case 'd': delete_books(); break;
            case 'w': write_catalogue(); break;
            case 'r': read_catalogue(); break;
            case 'q': return;
            default : 
                {
                    cout << "Please, enter a correct command." << endl;
                    system("pause");
                }
        }

    } while(true);
}

void main()
{
    menu();

}

Answer 1

Your global aux is a constant pointer to one BOOK – aux[0] and no more. You can not copy more than one BOOK hier.
You redefine a local aux, with hide the global. What you put there is “leak” after the functions new_book() returned.

Use std::string and containers, and don’t abuse pointers and global variables.