Library Management System using Virtual Functions in C++

#include<iostream>
#include<conio.h>
#include<string>
using namespace std;

int isbn2,index;
int search(int isbn);
int nstaff=0,nstud=0,bkid=0;
class library
{
public:
virtual int returnbook(){return 0;}
virtual int takebook(){return 0;}
virtual void addbook(){}
virtual void addstaff(){}
virtual void adds(){}
virtual int isb(){return 0;}
virtual string str(){return"";}
virtual int sto(){return 0;}
};

library *stud[100],*sta[100],*bks[100];

class library_store:public library
{
public:
string bookname;
int isbn;
int stock;
library_store():stock(0)
{ }

int isb(){return isbn;}
string str(){return bookname;}
int sto(){ return stock;}

int returnbook()
{
stock++;
return 1;
}
int takebook()
{
if(stock>0)
{
stock--;
return 1;
}
else
{
cout<<"\nThe books are not available!!!";
return -1;
}
}
void addbook()
{
cout<<"Enter name of the book: ";
cin>>bookname;
cout<<"Enter book number: ";
cin>>isbn;
cout<<"Enter number of books available: ";
cin>>stock;
}

};

class staff:public library
{
public:
string name;
int bookstaken;


int returnbook()
{
int days;
cout<<"\nEnter book number: ";
cin>>isbn2;
index=search(isbn2);
if(index!=-1)
{
cout<<"\nEnter the number of days since the book was borrowed: ";
cin>>days;
cout<<"\nExtra fees to be paid: Rs."<<(days-10)*1;
return bks[index]->returnbook();
}
else
return -1;
}
int takebook()
{
cout<<"\nEnter Book number: ";
cin>>isbn2;
index=search(isbn2);
if(index!=-1)
{
cout<<"\nPlease return the book within 10 days!!!";
return bks[index]->takebook();
}
else
return -1;
}
void addstaff()
{
cout<<"\nEnter the name of the staff:";
cin>>name;
}
};

class students:public library
{
public:
string name;

int returnbook()
{
int days;
cout<<"\nEnter book number: ";
cin>>isbn2;
index=search(isbn2);
if(index!=-1)
{
cout<<"\nEnter the number of days since the book was borrowed: ";
cin>>days;
cout<<"\nExtra fees to be paid: Rs."<<(days-5)*1;
return bks[index]->returnbook();
}
else
return -1;
}
int takebook()
{
cout<<"\nEnter the book number: ";
cin>>isbn2;
index=search(isbn2);
if(index!=-1)
{
cout<<"\nPlease return the book within 10 days!!!";
return bks[index]->takebook();
}
else
return -1;
}
void adds()
{
cout<<"\nEnter the name of the student:";
cin>>name;
}
};

void display()
{
cout<<"\nThe available books are:\n\nISBN\t-\tName\t-\tStock\n";
for(int i=0;i<bkid;i++)
{
cout<<"\n"<<bks[i]->isb()<<"\t-\t"<<bks[i]->str()<<"\t-\t"<<bks[i]->sto();
}
}

void staf()
{
int ch,id,rep=1;
system("cls");

cout<<"\nEnter staff library number: ";
cin>>id;
id--;
while(rep==1)
{
system("cls");
cout<<"\nSTAFF\n-----\n";
cout<<"\n1.Display books\n2.Take book\n3.Return book\n4.Go to main menu\n";
cin>>ch;
switch(ch)
{
case 1:
display();
break;
case 2:
if(sta[id]->takebook()==-1)
cout<<"\nInvalid Number!!!";
else
cout<<"\nPlease wait...";
break;
case 3:
if(sta[id]->returnbook()==-1)
cout<<"\nInvalid Number!!!";
else
cout<<"\nPlease wait...\n";
break;
case 4:
rep=0;
break;
}
getch();
}
}

void student()
{
int ch,id,cont=1;
system("cls");
cout<<"\nSTUDENT\n--------\n";
cout<<"Enter library number: ";
cin>>id;
id--;
while(cont==1)
{
system("cls");
cout<<"\n1.Display books\n2.Take books\n3.Return book\n4.Go to main menu\n";
cin>>ch;
switch(ch)
{
case 1: display();
break;

case 2: if(stud[id]->takebook()==-1)
cout<<"\nInvalid Number!!!";
else
cout<<"\nPlease wait...\n";
break;

case 3: if(stud[id]->returnbook()==-1)
cout<<"\nInvalid Number!!!";
else
cout<<"\nPlease wait...\n";
break;

case 4: cont=0;
break;
}
getch();
}
}

void admin()
{
int ch,rep=1;
system("cls");
while(rep==1)
{
system("cls");
cout<<"\nDATABASE\n---------\n\n1.Add staff\n2.Add student\n3.Add books\n4.Display\n5.Exit\n";
cin>>ch;
switch(ch)
{
case 1: sta[nstaff]=new staff;
sta[nstaff]->addstaff();
nstaff++;
cout<<"\nThe Library number is: "<<nstaff;
break;

case 2: stud[nstud]=new students;
stud[nstud]->adds();
nstud++;
cout<<"\nThe Library number is: "<<nstud;
break;

case 3: bks[bkid]=new library_store;
bks[bkid]->addbook();
bkid++;
break;

case 4: display();
break;

case 5: rep=0;
break;
}
cout<<"\nPress Enter to continue:";
getch();
}
}

int search(int isbn)
{
for(int i=0;i<bkid;i++)
{
if(bks[i]->isb()==isbn)
return i;
}
cout<<"No book found!!!";
return -1;
}

void main()
{
int choice,cont=1;
while(cont==1)
{
cout<<"\n1.Administrator\n2.Staff\n3.Student\n4.Exit\nEnter your choice: ";
cin>>choice;
switch(choice)
{
case 1: admin();
break;

case 2: staf();
break;

case 3: student();
break;

case 4: cont=0;
break;

default: cout<<"\n\nInvalid Entry!!";
}
}
}