#include <stdio.h>

#define MAXLEN 100

typedef struct {
   char element[MAXLEN];
   int front;
   int back;
} queue;

queue init ()
{
   queue Q;

   Q.front = 0;
   Q.back = MAXLEN - 1;
   return Q;
}

int isEmpty ( queue Q )
{
   return (Q.front == (Q.back + 1) % MAXLEN);
}

int isFull ( queue Q )
{
   return (Q.front == (Q.back + 2) % MAXLEN);
}

char front ( queue Q )
{
   if (isEmpty(Q)) {
      fprintf(stderr,"front: Queue is empty\n");
      return '\0';
   }
   return Q.element[Q.front];
}

queue enqueue ( queue Q , char ch )
{
   if (isFull(Q)) {
      fprintf(stderr,"enqueue: Queue is full\n");
      return Q;
   }
   ++Q.back;
   if (Q.back == MAXLEN) Q.back = 0;
   Q.element[Q.back] = ch;
   return Q;
}

queue dequeue ( queue Q )
{
   if (isEmpty(Q)) {
      fprintf(stderr,"dequeue: Queue is empty\n");
      return Q;
   }
   ++Q.front;
   if (Q.front == MAXLEN) Q.front = 0;
   return Q;
}

void print ( queue Q )
{
   int i;

   if (isEmpty(Q)) return;
   i = Q.front;
   while (1) {
      printf("%c", Q.element[i]);
      if (i == Q.back) break;
      if (++i == MAXLEN) i = 0;
   }
}

int main ()
{
   queue Q;

   Q = init(); printf("Current queue : "); print(Q); printf("\n");
   Q = enqueue(Q,'h'); printf("Current queue : "); print(Q); printf("\n");
   Q = enqueue(Q,'w'); printf("Current queue : "); print(Q); printf("\n");
   Q = enqueue(Q,'r'); printf("Current queue : "); print(Q); printf("\n");
   Q = dequeue(Q); printf("Current queue : "); print(Q); printf("\n");
   Q = dequeue(Q); printf("Current queue : "); print(Q); printf("\n");
   Q = enqueue(Q,'c'); printf("Current queue : "); print(Q); printf("\n");
   Q = dequeue(Q); printf("Current queue : "); print(Q); printf("\n");
   Q = dequeue(Q); printf("Current queue : "); print(Q); printf("\n");
   Q = dequeue(Q); printf("Current queue : "); print(Q); printf("\n");
}