Linked Listing [GELACIO]/[PULAN]

#include<conio.h>
#include<iostream>
#include<fstream>
#include<Windows.h>
#include<dos.h>
#include<cctype>
#include<sstream>
#include<string>
using namespace std;
bool check = true;
struct node
{
 string name;
 int grade;
 node *next;
}*head,*lastptr;


void display(struct node* head, char Cchoice,int Igrade)
    {
          struct node *temp = head;
          cout <<"\n\nList elements are - \n";
          while(temp != NULL)
          {
            switch(toupper(Cchoice))
            {
                case 'A':
                if (temp->grade==Igrade)
                {
                cout << "Name: " << temp->name<<endl;
                cout << "Grade: " << temp->grade<<endl;
                } break;
                case 'B':
                if (temp->grade>Igrade)
                {
                cout << "Name: " << temp->name<<endl;
                cout << "Grade: " << temp->grade<<endl;
                }break;
                case 'C':
                if (temp->grade<Igrade)
                {
                cout << "Name: " << temp->name<<endl;
                cout << "Grade: " << temp->grade<<endl;
                }break;
                default:
                cout << "Name: " << temp->name<<endl;
                cout << "Grade: " << temp->grade<<endl;

            }
            temp = temp->next;

            }
    }

void add()
{
 node *p;
 p=new node;
 cout<<"Enter name of student: "<<endl;
 cin>> p->name;

 cout<<"Enter Grade: "<<endl;
 cin>>p->grade;

 p->next=NULL;

 if(check)
 {
  head = p;
  lastptr = p;
  check = false;
 }
 else
 {
  lastptr->next=p;
  lastptr=p;
 }
 cout<<endl<<"Recorded"<<endl;
 getch();
}



int main()
{
 char x;
 cout<<"\t\t ******************************* \t\t\t"<<endl;
 cout<<"\t\t ***STUDENT MANAGEMENT SYSTEM*** \t\t\t"<<endl;
 cout<<"\t\t ******************************* \t\t\t"<<endl<<endl;

 getch();
 char choice = 'X', Cchoice = 'X', Nchoice = 'X';
 int i=0, Igrade=0;
 while (toupper(choice)!='N')
    {
        add(); i++;
        cout<<"More Entry [Y] / [N]: "; cin>>choice;
    }

    while (toupper(Nchoice)!='N')
    {
        cout << "Criteria for displaying the list: "<<endl;
        cout << "A. Grade =\nB. Grade >\nC. Grade < \n D. All\n";
        cout << "Enter Choice (A-D): "; cin>>Cchoice;
        if(toupper(Cchoice)!='D')
        {
        cout << "Grade: ";cin>>Igrade;
        }
        display(head, Cchoice, Igrade);
        cout<<"More Entry [Y] / [N]: "; cin>>Nchoice;
    }
    system("pause");
    return 0;
}