queue.c

/* 
  Below program is written in "C" language. This is a sample implementation of simple Queue.
*/

#include<stdio.h>
#include<process.h>
#include<stdlib.h>

#define SIZE 10

int a[SIZE];
int rear;   //rear is same as tail; front - same as head
int rear = front = -1;  

// declaring enqueue, dequeue and display functions
void enqueue(int x);     
int dequeue();
void display();


// function enqueue - to add data to queue
void enqueue(int x)
{
    if(front == -1) {
        front++;
    }
    if( rear == SIZE-1)
    {
        printf( "Queue is full");
    }
    else
    {
        a[++rear] = x;
    }
}
// function dequeue - to remove data from queue
int dequeue()
{
    return a[++front];  // following approach [B], explained above
}

// function to display the queue elements
void display()
{
    int i;
    for( i = front; i <= rear; i++)
    {
        printf( a[i] );
    }
}

// the main function
int main()
{
    enqueue(10);
    enqueue(100);
    enqueue(1000);
    enqueue(1001);
    enqueue(1002);
    dequeue();
    enqueue(1003);
    dequeue();
    dequeue();
    enqueue(1004);

    display();
    return 0;
}