please help me correct this error. [Error] 'clrscr' was not declared in this scope (it picks questions and answers from an external file)

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

string questions[50];
string str;

class contest
{

private:
  int roll;
  float x;
  char name[50];
  char s[100],ans;

 public:
 contest()
 { x=0; }
 void init();
 void define();
 void display();
 };
 void  contest :: define()

 {
ifstream in;
  char a;
  int i=0;

  in.open("questions.txt");
  while(in.eof()==0)
 {
 in.getline(s,100);
 cout<<endl<<s;
if(i==5)
{
in.get(a);
cout<<"\nans:";
 cin>>ans;
i=-1;
if(ans==a)
   {
   x=x+5;
   cout<<" *Your ans  correct.\n";
   }
 else
   {
   if(x>0)
    x=x-2.5;
   cout<<" # Wrong ans.\n";
   }
 }
  i++;
  }
 in.close();
 }
  void contest :: init()
   {
 cout<<"\t\t\t   Student Name:";
 cin>>name;
 cout<<"\t\t\t   Index Number:";
 cin>>roll;
   }
 void contest :: display()
   {
 cout<<"\n **Result:\n";
 cout<<"\t"<<name<<" you got total "<<x<<" marks, out of 50.\n";
   }

 int main()
{
  clrscr();
  contest r;
  cout<<"      \t\t\t     QUIZ    \t      Total Marks:50\n\n";
  r.init();
  cout<<"\t*5 marks per Ques(half negative marking for wrong ans)";
   L:
  cout<<"\n\n\tselect your choice:\n"
    <<"\n\tTo start Quiz Press 1"
    <<"\n\tTo quit Press 0        :";
   int c;
   cin>>c;
   switch(c)
   {
   case 1:
    r.define();
    r.display();
    break;
   case 0:
    exit(1);
   default:
    cout<<"invalid choice!";
    goto L;
   }
   getch();
   }