StaticQueueUsingC

/******************************************************************************
 Static Queue : means queue using array. size of queue is fixed in advance like array, 
 thats why we can only add number of elements equal to size of queue.    
*******************************************************************************/

#include<stdio.h>
#include<conio.h>
#define size 4                 // define size of queue, as per our requirement
int queue[size];               // declare array for queue
int front = -1;                // Initialy as queue is emepty, set front to -1
int rear = -1;                 // Initialy as queue is emepty, set rear to -1

// enQueue => Adding element in queue, at rear end of queue
void enQueue(int value)
{
   // Before adding element check for full, if rear is equal to size-1 means queue is full
    if ( rear == size-1 )
    {
        printf("Queue is full, we can not insert");
    }
    else
    {
        if ( front == -1 )
        {
            //At first insertion move both to 0, Otherwise while deleting element it may say empty queue(as front reamins -1)
            front = 0;
            rear = 0;
        }
        else
        {
           // Otherwise only increment rear
           rear++; 
        }        
        queue[rear] =  value;
    }
}

// enQueue => Deleting element from queue, from front end 
void deQueue()
{
    // Before deleting an element check for empty, if front is equal to -1 means queue is empty
    if ( front == -1 )
    {
        printf("Queue is empty, we can not delete");
    }
    else
    {
        printf("Deleted Value %d",queue[front]);          // display deleted element
        if ( front == rear )
        {
            //When front == rear, means last element in queue, so after deleteing last element, make both front & rear = -1 
            front = -1;
            rear = -1;
        }
        else
        {
           //Otherwise means there are more elements to delete, so just move front to next element
           front++; 
        }
    }
}

void displayQueue ()
{
  int i;
  if (front == -1)
  {
      printf ("Queue is empty");
  }
  else
  {
      printf ("Queue : |");
      for (i = front; i <= rear; i++)
	     {
	       printf (" %d |", queue[i]);
	     }
    }
}

void main()
{
    clrscr();
    enQueue(10);
    enQueue(20);
    deQueue();
    enQueue(30);
    enQueue(40);
    enQueue(50);
    enQueue(60);
    deQueue();
    deQueue();
    deQueue();
    deQueue();
    deQueue();
    deQueue();
    getch();
}