implemented queue using stack

queue.c

#include <stdio.h>
#include <stdlib.h>
struct qnode
{
 int data;
 struct qnode *next;
};
typedef struct qnode* qptr;
qptr front=NULL,rear=NULL;
int isempty(front)
{
if(front==NULL)
return 0;
return 1;
}
qptr push(qptr rear,int data)
{
  qptr p;
  p=(qptr)malloc(sizeof(struct qnode));
  p->data=data;
  p->next=NULL;
  if(rear==NULL)
  {
    rear=p;
    front=p;
    return p;
  }
  rear->next=p;
  rear=p;
  return rear;
}
qptr pop()
{
   qptr t;
   if(isempty(front))
   {
   t=front;
   front=front->next;
   return t;
   }
   printf("queue is empty...! ");
   exit(1);
}
int main()
{
    qptr t=NULL;
    int c,data;
    while(1)
    {
    scanf("%d",&c);
    if(c==1)
    {
      scanf("%d",&data);
      rear=push(rear,data);
    }
    else if(c==0)
    {
      t=pop();
      printf("%d\n",t->data);
    }
    else{
    exit(1);
    }
    }
    return 0;
}