C++ program for the application of QUEUE

#include<iostream>
#include<conio.h>
#include<process.h>
using namespace std;
int f,r,q[50],n;
class queue
{
public:

void insert();
void deletion();
void front();
void rear();
void display();
void clearq();
void qsize();
};

void queue::insert()
{ int item;
if(r==(n-1))
{
cout<<"\n queue overflow";
}
else
{
if(r==-1 &&f==-1)
{
f=0;
r=0;
}
else
{
r++;
}
cout<<"\n enter the item to enter ";
cin>>item;
q[r]=item;
}

}
void queue::deletion()
{
int item;

if(f>r||(f==-1&&r==-1))
{
cout<<"\n underflow";
f=-1;
r=-1;
}
else
{
item=q[f];
f=f+1;
cout<<"\n deleted item ="<<item;
}
}
void queue::front()
{
if(f>r||(f==-1&&r==-1))
cout<<"\n underflow";
else
cout<<"\n queue front="<<q[f];
}
void queue::rear()
{
if(r>=n)
cout<<"\n overflow";
else
cout<<"\n queue rear="<<q[r] ;
}

void queue::display()
{
int i;
if(f==-1)
cout<<"\n no element element has been inserted";
else
{
for(i=f;i<=r;i++)

cout<<"|"<<q[i]<<"|";

}
}
void queue::clearq()
{
if(f>r)
cout<<"\n no element inserted";
else
{
q[r]='\0';
}
f=-1;
r=-1;
}
void queue::qsize()
{ int size;
if(f==-1&&r==-1)
cout<<"\n the queue is empty";
else
{
size=(r-f)+1;
cout<<"\n size of queue is="<<size;
}
}
void main()
{ f=-1;
r=-1;
int w=1,ch;
queue q1;
system("cls");
cout<<"\n ENTER THE MAXIMUM SIZE OF THE QUEUE";
cin>>n;
while(w==1)
{
system("cls");
cout<<"\n WELCOME TO THE MENU ";
cout<<"\n ====================================================";
cout<<"\n 1.To insert an element into the queue \n 2.To delete an element from the queue \n 3.To display front of the queue \n 4.To dispaly the rear of the queue \n 5.To display the elements in the queue \n 6.TO clear the queue \n 7.To show the size of the queue \n 8.exit";
cout<<"\n ===================================================";
cout<<"\n PLEASE ENTER ANY OF THE ABOVE CHOICE ";
cin>>ch;
switch(ch)
{
case 1:q1.insert();
break;
case 2:q1.deletion();
break;
case 3:q1.front();
break;
case 4:q1.rear();
break;
case 5:q1.display();
break;
case 6:q1.clearq();
cout<<"\n the queue has been cleared";
break;
case 7:q1.qsize();
break;
case 8:exit(0);
break;
default: cout<<"\n invalid entry";
}
cout<<"\n press (1) to continue or any other digit to exit";
cin>>w;
}
}