This document describes a C implementation of a queue using a linked list. It defines a queueNode struct with data and next pointer fields and a queue struct with front and rear pointers. Functions are provided to initialize an empty queue, check if a queue is empty, add elements to the rear, remove elements from the front, and print the queue. The main function demonstrates using the queue by adding and removing elements and printing the queue.

1. /*
Linked List Implementation of the Queue in C
Author: Kasun Ranga Wijeweera
Email: krw19870829@gmail.com
Date: 20130514
*/
#include<stdio.h>
#include<conio.h>
#include<alloc.h>
typedef struct queueNode *link;
struct queueNode
{
int data;
link next;
};
typedef struct
{
link front;
link rear;
}queue;

2. void initQueue(queue *q)
{
q->front=NULL;
q->rear=NULL;
}
int isEmpty(queue *q)
{
if((q->front)==NULL)
{
return 0;
}
else
{
return 1;
}
}
void putQueue(queue *q,int x)
{
link t=(link)malloc(sizeof(struct queueNode));
t->data=x;
t->next=NULL;

3. if(isEmpty(q))
{
q->rear->next=t;
q->rear=t;
}
else
{
q->front=t;
q->rear=t;
}
}
int getQueue(queue *q)
{
link t=q->front;
int x=t->data;
if((q->front)==(q->rear))
{
q->front=NULL;
q->rear=NULL;
}
else
{

4. q->front=t->next;
}
free(t);
return x;
}
void printQueue(queue *q)
{
link t=q->front;
while(t!=NULL)
{
printf("%d ",t->data);
t=t->next;
}
}
void main()
{
queue *q;
int x;
clrscr();

5. q=(queue*)malloc(sizeof(queue));
initQueue(q);
putQueue(q,10);
putQueue(q,20);
putQueue(q,30);
putQueue(q,40);
putQueue(q,50);
printf("n");
printQueue(q);
if(isEmpty(q))
x=getQueue(q);
printf("n");
printQueue(q);
putQueue(q,60);
putQueue(q,70);
printf("n");
printQueue(q);
getch();

6. }