C programs for Double ended queue ADT Using Array

1			#include<stdio.h>
2			#include<stdlib.h>
3			#define MAXSIZE 4
4			int Queue[MAXSIZE],rear=-1,front=-1,i;
5			void insert_at_front();
6			void insert_at_rear();
7			void delete_at_front();
8			void delete_at_rear();
9			void display();
10			int main()
11			{
12			int ch;
13			printf("\n 1.insert at front\n 2.insert at rear\n\n 3.delete at front\n4.delete at rear\n5.DISPLAY\n\n
14			6.EXIT\n");
15			do
16			{
17			printf("\n\tenter_your_choice[1-6]:");
18			scanf("%d",&ch);
19			switch(ch)
20			{
21			case 1:insert_at_front();
22			break;
23			case 2:insert_at_rear();
24			break;
25			case 3:delete_at_front();
26			break;
27			case 4:delete_at_rear();
28			break;
29			case 5:display();
30			break;
31			case 6:exit(0);
32			default:printf("invalid_option \n");
33			}
34			}while(1);
35			}
36			void insert_at_rear()
37			{
38			if(rear==MAXSIZE-1)
39			{
40			printf("queue_is_full(overflow)\n");
41			return;
42			}
43			rear++;
44			printf("enter_the_element_to_insert_at_rear:");
45			scanf("%d",&Queue[rear]);
46			if(front==-1)
47			front++;
48			}
49			void insert_at_front()
50			{
51			int num;
52			if(front<=1)
53			{
54			printf("\n Can't add_item at front_end");
55			return;
56			}
57			else
58			{
59			front--;
60			printf("\n Enter_item to insert:");
61			scanf("%d",&Queue[front]);
62			}
63			}
64			void delete_at_front()
65			{
66			if(front==-1)
67			{
68			printf("queue_is empty(underflow)\n");
69			return;
70			}
71			printf("the_delete_at_front_element is:%d \n",Queue[front]);
72			if(front==rear)
73			front=rear=-1;
74			else
75			front++;
76			}
77			void delete_at_rear()
78			{
79			if(rear==-1)
80			{
81			printf("queue_is empty(underflow)\n");
82			return;
83			}
84			printf("the_delete_at_rear element is:%d \n",Queue[rear]);
85			if(front==rear)
86			front=rear=-1;
87			else
88			{
89			rear--;
90			}
91			}
92			void display()
93			{
94			if(front==-1)
95			{
96			printf("queue_is empty(underflow)\n");
97			return;
98			}
99			printf("the_element_in_queue are:front->");
100			for(i=front;i<=rear;i++)
101			printf("%d ",Queue[i]);
102			printf("<-REAR\n");
103			}
			Output
			1.insert at front
			2.insert at rear
			3.delete at front
			4.delete at rear
			5.DISPLAY
			6.EXIT
			enter_your_choice[1-6]:2
			enter_the element_to_insert_at_rear:10
			enter_your_choice[1-6]:2
			enter_the element_to_insert_at_rear:30
			enter_your_choice[1-6]:5
			the_element in_queue are:front->10 30 <-REAR
			enter_your_choice[1-6]:2
			enter the element to insert_at_rear:40
			enter_your_choice[1-6]:5
			the_element in_queue are:front->10 30 40 <-REAR
			enter_your_choice[1-6]:3
			the delete_at_front element is:10
			enter_your_choice[1-6]:5
			the_element in_queue are:front->30 40 <-REAR
			enter_your choice[1-6]:1
			Enter_item to insert:40
			enter_your_choice[1-6]:5
			the_element in queue are:front->40 30 40 <-REAR
			enter_your_choice[1-6]:4
			the_delete_at_rear element is:40