0 Program Queue C++

#include<iostream.h>
#include<conio.h>
#include<stdio.h>
#include<stdlib.h>
#include<process.h>
#define maxsize 5
 
struct que
{
   int items[maxsize];
   int rear , front;
};
 
void insert(struct que *,int);
int remove(struct que *) ;
int empty (struct que *);
void makenull(struct que *);
void front(struct que *);
 
 
 /****************** insert function **********************/
 
void insert(struct que *q,int a)
 
 {
 
  if(q->rear==maxsize-1)
 
     q->rear=0;
 
  else
 
     (q->rear)++ ;
 
 if(q->rear==q->front)
   {
 
  cout<<endl<<"OVERFLOW" <<endl ;
     //exit(1);
   }
 
    q->items[q->rear]=a ;
 
 
 }
 
  /*************** remove function ********************/
 
int remove(struct que *q)
  {
 
   if(empty(q))
 
    {
  cout<<endl<<" UNDERFLOW"<<endl;
 
    }
 
  if(q->front==maxsize-1)
 
    q->front =0;
 
    else
    {
   (q->front)++;
    }
    return (q->items[q->front]);
 
 q->rear=q->front=maxsize-1;
 
  }
 
 
 /********************** empty function ************************/
 
 int empty(struct que *q)
    {
 
 
    if(q->front==q->rear)
 
   return (1);
 
  else
 
   return (0);
 
  }
/********************* front function ******************************/
//returns the 1st element in queue
void front(struct que *q)
 
{
 int a;
 
 int first_val;
 
 
 first_val=q->items[q->front];
 
 cout<<endl<<"FIRST ELEMENT IS :" <<first_val;
 }
 
  /******************** makenull function ***************************/
 
 void makenull(struct que *q)
 
 {
 if(empty(q))
 
  {
 
     cout<<"THE QUEUE  IS EMPTY";
  }
 
   else
 
  {
 
     q->rear=q->front=maxsize-1;
 
     cout<<endl<<"QUEUE Is EMPTY "<<endl ;
  }
 
 }
 
 
 /****************** main function *****************************/
 
void main ()
 
{
 
 int a;
 clrscr();
 struct que *q;
 
 
 for(int i=0;i<maxsize;i++)
 q->items[i]=0;
 
   char  choice;
   q->rear=q->front=maxsize-1;
   cout<<endl<<"******************* IMPLIMENTATION OF QUEUES******************" <<endl<<endl;
 
 do
 
 
 { //clrscr();
 
 
 cout<<endl<<endl<<" 1 : Insert "<<endl<<" 2 : Remove "<<endl<<" 3 : check empty : 0 shows  not empty & 1  shows  empty " <<endl<<" 4 : Makenull"<<endl<<" 5 : Front"<<endl;
 cout<<                          "enter ur choice : " ;
 
 choice=getche();
 
   switch(choice)
 
    {
 
   case '1' :
 
      {
 
     cout<<endl<<"ENTER THE VALUE : ";
     cin>>a;
 
     insert(q,a);
 
     for(int i=0; i<=maxsize-2;i++)
 
     cout<<q->items[i]<<" ";
 
     break;
 
      }
 
   case '2' :
 
      {
      cout<<endl<<"THE VALUE IS: ";
 
     cout<<remove(q)<<endl;
 
     for(int i=maxsize-1;i>0;i--)
 
     cout<<q->items[i]<<" ";
 
     break;
 
      }
 
 
 
   case '3' :
 
      {
 
     cout<<endl<<empty(q);
 
     break;
 
      }
 
   case '4' :
 
      {
 
     makenull(q);
 
      for(int i=0;i<maxsize;i++)
     {
 
     q->items[i]='\0';
 
     cout<<q->items[i]<<endl;
 
      }
 
      break;
 
      }
 
   case '5':
 
    {
 
        front(q);
 
        break;
    }
 
 
     default :
 
 
 
     cout<<"  wrong choice  ";
     break;
 
    }//end of switch
 
 cout<<endl<<"Do u want to exit y/n :" ;
 
    } //end do while
 
 while((choice=getche())!='y');
 
 }//end main