issue in double linklist

[Jun77]

what is the problm in this code,,,

gives me error at Modify function,

 #include<iostream>
#include<conio.h>
#include<cstdlib>
#include<windows.h>
#include<iomanip>
using namespace std;
struct node
{
	 int roll_no;
   string name;
   char grade;
 int  p_m ,c_m,m_m,cs_m,e_m;
 int num;
   float per;
   
	node* next;
	node* pre;
}*first,*last;

class linklist
{
  public:
  	
  	linklist()
  	{
  		first=NULL;
  		last=NULL;
  	}
  	
	  void insert(int Roll_no,string Name,char grade,int P_m,int C_m,int M_m,int CS_m,int E_m);
  	void Delete(int D);
  	void search(int S);
  	void Modify(string na);
  	void show();
  	


};
char calculate( int p_m ,int c_m ,int m_m ,int  e_m ,int cs_m)
{	

	int per=(p_m +c_m +m_m + e_m + cs_m)/5;
	if(per>=60)
		return 'A';
	else if(per>=50)
		return 'B';
	else if(per>=33)
		return 'C';
	else
		return 'F';
}



void linklist::insert(int Roll_no,string Name,char grade,int P_m,int C_m,int M_m,int CS_m,int E_m)
{
	node* ptr=new node;
	ptr->roll_no=Roll_no;
	ptr->name=Name;
	ptr->p_m=P_m;
	ptr->c_m=C_m;
	ptr->m_m=M_m;
	ptr->cs_m=CS_m;
	ptr->e_m=E_m;
	ptr->grade=grade;
	
	if(first==NULL)
	{
		ptr->next=NULL;
		ptr->pre=NULL;
	   first=last=ptr;
	}
	else
	{
		ptr->pre=last;
		ptr->next=NULL;
		last=ptr;
		(ptr->pre)->next=last;
	}
}
/////////////////////////////////

void linklist::Delete(int r_no)
 {
	node* ptr=first;
  while(ptr !=NULL)
	{
      if(ptr->roll_no == r_no)
      {
      	if(ptr->next == NULL && ptr->pre == NULL)
      	{
      		first=NULL;
      		last=NULL;
      	//	delete ptr;
      		free(ptr);
      		 cout<<"\nRecord Deleted ";
			  break;
      	}
      	else if(ptr->next == NULL)
      	{
      		last=ptr->pre;
      	    (ptr->pre)->next=NULL; 
		//	 delete ptr;
			free(ptr);
			 cout<<"\nRecord Deleted ";	
			break;
      	}
      	else if(ptr->pre == NULL)
      	{
      		first=ptr->next;
      		(ptr->next)->pre=NULL;
			delete ptr;
			 cout<<"\nRecord Deleted ";
		//	free(ptr);
      	    break;
		  }
      	else
      	{
      		(ptr->next)->pre=ptr->pre;
      		(ptr->pre)->next=ptr->next;
      		delete ptr;
      		 cout<<"\nRecord Deleted ";
      		//free(ptr);
      	    break;
		  }
      	
      }
    ptr=ptr->next;
 }
 

    cout<<"Rocord "<<r_no<<" not found in the list"<<endl;
}

///////////////////////////


void linklist::search(int D)
{
	node *s=first;
	while(s != NULL)
	{
		if(s->roll_no ==D)
		{
		
			cout<<"\nRoll number of student : "<<s->roll_no;
	cout<<"\nName of student : "<<s->name;
	cout<<"\nMarks in Physics : "<<s->p_m;
	cout<<"\nMarks in Chemistry : "<<s->c_m;
	cout<<"\nMarks in Maths : "<<s->m_m;
	cout<<"\nMarks in English : "<<s->e_m;
	cout<<"\nMarks in Computer Science :"<<s->cs_m;
	cout<<"\nPercentage of student is  :"<<s->per;
	cout<<"\nGrade of student is :"<<s->grade;

		}
		s=s->next;
	}
	cout<<"\n\t\t NOT FOUND \n";
}

void linklist::show()
{
	system("cls");
	 int counter=0;
	node* s=first;
	  cout<<"\n\n\t\tSTUDENT RECORD : \n"<<endl;
	while(s !=NULL)
	{
		
		counter ++;
		cout<<"====  STUDENT NUMBER  ==== "<<counter;
		cout<<"\n____________________________\n"
		 ; cout<<"\nRoll number of student : "<<s->roll_no;
	cout<<"\nName of student : "<<s->name;
	cout<<"\nMarks in Physics : "<<s->p_m;
	cout<<"\nMarks in Chemistry : "<<s->c_m;
	cout<<"\nMarks in Maths : "<<s->m_m;
	cout<<"\nMarks in English : "<<s->e_m;
	cout<<"\nMarks in Computer Science :"<<s->cs_m;
	cout<<"\nPercentage of student is  :";
	cout<<"\nGrade of student is :"<<s->grade;
	
    cout<<"\n===================================================\n";
		s=s->next;
	}
}

///////////
int main()
{ 

	int roll_no,choice;
   string name
   ;char grade;
 int  p_m ,c_m,m_m,cs_m,e_m;
 int num;
 int student;
   float per;
	
	linklist obj;
	
	cout<<"\n\n\t\t";
	system("pause");
	while(1)
	{
		system("color 72");
		system("cls");
    cout<<"======================================";
    cout<<"*******  STUDENT REPORT CARD  ********";
	cout<<"======================================";
    
	cout<<"\t[1]  #  ADD Student Recprd\n";
    cout<<"\t[2]  #  DELETE STUDENT RECORD\n";
    cout<<"\t[3]  #  Search By Roll No. \n";
    cout<<"\t[4]  #  DISPLAY All Student RECORD\n";
    cout<<"\t[5]  #  Modify Student RECORD\n";
    cout<<"\t[6]  #  Exit program \n";
cin>>choice;
switch(choice)
{
	case 1:
	{
		system("cls");
		system("color 75");
		cout<<"\n\t\t\tEnter number of student Records:";
		cin>>student;
   	 	  int s1=1;
		
			  while(s1<=student)
			  {
			  	cout<<"\nRoll number of student ";
	cin>>roll_no;
	cout<<"\n\nName of student ";
	cin>>name;
	cout<<"\nmarks in physics out of 100 : ";
	cin>>p_m;
	cout<<"\nmarks in chemistry out of 100 : ";
	cin>>c_m;
	cout<<"\nmarks in maths out of 100 : ";
	cin>>m_m;
	cout<<"\nmarks in english out of 100 : ";
	cin>>e_m;
	cout<<"\nmarks in computer science out of 100 : ";
	cin>>cs_m;
				  
			grade=calculate(p_m, m_m, e_m,c_m, cs_m);	
			obj.insert(roll_no,name,grade,p_m,c_m,m_m,e_m,cs_m);
			  	s1+=1;
	          }
		break;
	}
	case 2:
	{
			system("color 73");
		if(first==NULL)
		{
		 cout<<"\nRECORD IS EMPTY ";
			cout<<"\n\n\t\t";
		   system("pause");
			break;
	    }
		cout<<"Enter roll no.: ";
		cin>>roll_no;
		obj.Delete(roll_no);
		cout<<"\n\n\t";
		system("pause");
		break;
	}
	case 3:
	{
			system("color 74");
			if(first==NULL)
		{
			char a[100]="\nRECORD IS EMPTY ";
	//	  slow(a);
			cout<<"\n\n\t\t";
		   system("pause");
		   break;
	   }
	   cout<<"\nEnter Roll No. to Search \n";
	   cin>>roll_no;
	   obj.search(roll_no);
	    cout<<"\n\n\t\t";
		system("pause");
		break;
	}
	case 4:
	{
			system("color 7C");
			if(first==NULL)
		{
	    cout<<"RECORD IS EMPTY";
	//	slow(a);
		cout<<"\n\n\t\t";
		system("pause");
		break;
	    }
		obj.show();
		cout<<endl<<endl<<"\t\t";
		system("pause");
		break;
	}
	case 5:
	{
			system("color 7D");
			if(first==NULL)
		{
	    cout<<"RECORD IS EMPTY ";
	cout<<"\n\n\t\t";
		system("pause");
		break;
	    }
	    cout<<"\nSearch By Name ( Update Record ): ";
	    cin>>name;
	    obj.Modify(name);
	    cout<<"\n\n\t\t";
		system("pause");
		break;
	}
	case 6:
	{
		exit(1);
		break;
	}
	default:
		{
				system("color 7E");
		 cout<<"\n\t\tPlease Enter Correct NUMBER \n\n";
}	
	
 } 	
getch();
return 0;	
}
 void linklist::Modify(string name)
{
	
  int roll_num;
  char grade;
  int  phy_m ,chem_m,math_m,coms_m,eng_m;
  int num;
  node* ptr=first;
while(ptr != NULL)
{
	if(ptr->name == name)
	{
		cout<<"\n\n";
			cout<<"roll num NO = ";
			  	cin>>roll_num;
				 ptr->roll_no=roll_num;
				  cout<<"\nSTUDENT NAME = ";
			  	  cin.get();
				  getline(cin,name);
				 		 ptr->name=name;
				 	cout<<"Markx in Physics";	 
				 	cin>>phy_m;
				 	ptr->p_m=phy_m;
				 	cout<<"Markx in chemistry ";
				 	cin>>chem_m;
				 	ptr->c_m=chem_m;
					 cout<<"Markx in Maths ";
					 cin>>math_m;
					 ptr->m_m=math_m;
					 cout<<"markx in english";
					 cin>>eng_m;
					 ptr->e_m=eng_m;
					 cout<<"markx in computer science";
					 cin>>coms_m;
					 ptr->cs_m=coms_m;
				
				 		 
	       	cout<<"\n\t\tRecord is updated : \n";
		break;
		}
ptr=ptr->next;
}	
cout<<"\n\t\tRECORD NOT FOUND \n";
}

[ne555]

If you bother yourself to indent your code properly, you'll see mismatched braces.