Code:
 
 /* Circular Queues */
#include<iostream.h>
#include<conio.h>
#include <stdlib.h>
#include <string.h>
const int MAX = 5;
class cqueue
{
      int a[MAX],front,rear;
      public :
     cqueue()
     {
    front=rear=-1;
     }
     void insert(char);  // THIS IS THE PROBLEM, I changed int to char
     int deletion();
     void display();
};
void cqueue :: insert(char TaxLic) // related
{
   if((front==0 && rear==MAX-1) || (rear+1==front))
     cout<<" Circular Queue is Full";
   else
   {
     if(rear==MAX-1)
     rear=0;
     else
    rear++;
     a[rear]=TaxLic; //related
   }
   if(front==-1)
     front=0;
   }
   int cqueue :: deletion()
   {
   int k;
   if(front==-1)
   cout<<"Circular Queue is Empty";
   else
   {
   k=a[front];
   if(front==rear)
      front=rear=-1;
   else
   {
      if(front==MAX-1)
      front=0;
      else
      front++;
   }
   }
   return k;
   }
   void cqueue :: display()
   {
    int i;
    if(front==-1)
    cout<<"Circular Queue is Empty";
    else
    {
    if(rear < front)
    {
    for(i=front;i<=MAX-1;i++)
       cout<<a[i]<<"   ";
    for(i=0;i<=rear;i++)
       cout<<a[i]<<"   ";
    }
    else
    {
    for(i=front;i<=rear;i++)
       cout<<a[i]<<"   ";
    cout<<endl;
    }
    }
   }
int main()
   {
   cqueue c1;
         char TaxLic [7];
         char Dname [20];
         char TaxTyp [15];
   int ch,val;
   char op;
   do
   {
     //clrscr();
     system("cls");
     cout<<"-----------Menu-------------\n";
     cout<<"1.Insertion\n";
           cout<<"2.Deletion\n";
           cout<<"3.Display\n";
           cout<<"4.Exit\n";
     cout<<"Enter Your Choice <1..4> ?";
     cin>>ch;
     switch(ch)
     {
      case 1 : cout<<"Enter Taxi License Number: ";
               fflush(stdin);    
                        gets(TaxLic);
      //cin>>val;
      
      c1.insert(TaxLic); // can't insert because of char type
      break;
      case 2 : val=c1.deletion();
      cout<<"Deleted Element :"<<val<<endl;
      break;
      case 3 : c1.display();
      break;
   }
   cout<<"Do you want to continue<Y/N> ?";
   fflush(stdin);
   cin>>op;
    }while(op=='Y' || op=='y');
     getch();
  }
I put a sign in it.. The coding is working but when i tried to change the date tyoe from int (TaxType) to char, it's not working..