Классы в С

#include "C:\USER\lab6\lab6.cpp"
#include <stdlib.h>
void main ()
{
library lib;
char ch;
l1:  clrscr();
  printf("\n\n\n\n\t\tHOME LIBRARY\n\n");
  printf("\n\n\n\n\t\tVuberete nugnoe deystvie:\n\n");
  printf("\t\t\t1.Add book\n");
  printf("\t\t\t2.Show book\n");
  printf("\t\t\t3.Search book\n");
  printf("\t\t\t4.Delete book\n");
  printf("\t\t\t5.Sort book\n");
  printf("\t\t\t6.Exit");
  ch=getch();
switch(ch){
     case '1': lib.add();goto l1;
     case '2': lib.show();goto l1;
     case '3': lib.find();goto l1;
     case '4': lib.del();goto l1;
     case '5': lib.sort();goto l1;
     case '6': exit(1);
     default : goto l1;
      }
}

#include <io.h>
#include <string.h>
#include <conio.h>
#include <stdio.h>
#include <stdlib.h>
#include <fstream.h>
class library {
public:
 char a[20];
 int y;
void add();
void del();
void find();
void sort();
void show();
};

void library :: add() {
clrscr();
char ch;
ofstream file("c:\\user\\lab6\\bi.txt",ios::app);
l1: printf("\n\nEnter Author:");
    cin>>a;
    printf("\n\nEnter Year:");
    cin>>y;
    file<<a<<" "<<y<<endl;;
    printf("\n\nBook ADDED");
    printf("\n\nMore?(y/n))");
ch=getch();
switch(ch) {
case 'y':goto l1;
default :break;
}
file.close();
}

void library :: show() {
clrscr();
printf("\n\n\tLIST LIBRARY\n\n");
ifstream file1("c:\\user\\lab6\\BI.TXT");
while (!file1.eof()){
     file1>>a>>y;
     cout<<"\t Author:"<<a<<"\t\t Year:"<<y<<endl;}
getch();
file1.close();
}
void library :: find() {
char b[20];
clrscr();
cout<<"\n\n\n\t\t\tWhat Authors to find?"; cin>>b;
ifstream file("c:\\user\\lab6\\bi.txt");
    while(!file.eof())
    {
     file>>a>>y;
     if(!strcmpi(a,b)){
     cout<<"\n\t"<<a<<"\t"<<y<<endl;}
    }
    getch();
}

void library :: del() {
[COLOR=RED]????????????????????[/COLOR]
}

void library :: sort(){
[COLOR=RED]????????????????????[/COLOR]
}