C Source code for Implementation of queue using Linked Lists

#define TRUE 1

#define FALSE 0

struct queue_element{

int data;

struct queue_element *next;

};

typedef struct queue_element queue_info;

typedef struct qpointer{

queue_info *front, *rear;

}queue;

queue *q;

queue *create()

{

queue *p;

p=(queue *)malloc(sizeof(queue));

p->front=NULL;

p->rear=NULL;

return(p);

}

int isempty(queue *q)

{

if(q->front == NULL)

return(TRUE);

else

return(FALSE);

}

void insert_queue (queue *q,int item)

{

queue_info *new;

new=(queue_info *) malloc (sizeof (queue_info));

new->next = NULL;

new->data = item;

if (isempty(q))

{

q->front = new;

q->rear = new;

}

else

{

q->rear->next=new;

q->rear=new;

}

return;

}

int delete_queue(queue *q)

{

int item;

queue_info *del;

if (isempty(q))

{

printf(“Queue is empty ! \n”);

return(-1);

}

else

{

del=q->front;

q->front=q->front->next;

item=del->data;

free (del);

if(q->front == NULL)

q->rear=NULL;

return(item);

}

}