Создать экземпляр класса без явного указания членов класса

    library();
    library(char *title="",char *author="",int year = 1900,int count = 1000);

library::library()
{
    title_="";
    author_="";
    year_=100;
    pcount_=-1;
}
 
library::library(char *title, char *author, int year, int count)
{
    title_=title;
    author_=author;
    year_=year;
    pcount_=count;
}

int main()
{
    library a();
    cout<<"Name: "<<a.getAuthor()<<endl;
    cout<<"Title: "<<a.getTitle()<<endl;
    cout<<"Year: "<<a.getYear()<<endl;
    cout<<"Count "<<a.getpCount()<<endl;
}

char *title="",char *author="",int year = 1900,int count = 1000

int main()
{
    library a();
    cout<<"Name: "<<a.getAuthor()<<endl;
    cout<<"Title: "<<a.getTitle()<<endl;
    cout<<"Year: "<<a.getYear()<<endl;
    cout<<"Count "<<a.getpCount()<<endl;
}

library a;

library::library()
{
    title_=new char[1];
    *title_=0; // пустая строка из 0 символов 
    author_=new char[1];
    *autor_=0;
    year_=100;
    pcount_=-1;
}
 
library::library(char *title, char *author, int year, int count)
{
    title_=new char[strlen(title)+1];
    strcpy(title_,title);
    author_=new char[strlen(autor)+1];
    strcpy(autor_,autor);
    year_=year;
    pcount_=count;
}

library(char *title,char *author="",int year = 1900,int count = 1000);

#include <iostream>
using namespace std;
class Foo
{
public: 
    Foo()
    {
        cout << "PRIVET KAK DELA" << endl;
    }
};
int main()
{
    Foo a();
}

library a;

library a{}; // без параметров

library a{"title", "author"}; // с параметрами

library * pa = new library{};

library * pa = new library{"title", "author"};