Implementation of queue enqueue and dequeue operations

#include<stdio.h>
void enque(int [100]);
void deque(int [100]);
void display(int [100]);
int front=-1,rear=-1;
main()
{
        int a[100],ch;
        do
        {
                printf("\n\n Enter the choice that you need \n");
                printf("\t1.ENQUE(insertion)\n\t2.DEQUE(deletion)\n\t3.DISPLAY\n\t4.EXIT\n\n");
                scanf("%d",&ch);
                switch(ch)
                {
                        case 1:enque(a);break;
                        case 2:deque(a);break;
                        case 3:display(a);break;
                        default:printf("\n\n\t Thank You!!!\n\n");break;
                }
        }while(ch<4);
}
void enque(int a[100])
{
        int item;
        if(front>100)
                printf("\n\n |QUEUE OVERFLOW| \n");
        else
        {
                printf("\n Enter element into the Queue: ");
                scanf("%d",&item);
                if(rear==-1)
                        front=0;
                rear++;
                a[rear]=item;
        }
}
void deque(int a[100])
{
        if(front==rear+1)
                printf("\n |QUEUE UNDERFLOW| \n");
        else
        {
                printf("\n Deleted element is %d \n",a[front]);
                front++;
        }
}
void display(int a[100])
{
        int i;
        if(rear==-1)
                printf("\n\n Queue is Empty \n\n");
        else
        {
                for(i=front;i<=rear;i++)
                        printf("\n\t%d",a[i]);
                printf("\n\n");
        }
}

Output :
 Enter the choice that you need
        1.ENQUE(insertion)
        2.DEQUE(deletion)
        3.DISPLAY
        4.EXIT

1

 Enter element into the Queue: 1


 Enter the choice that you need
        1.ENQUE(insertion)
        2.DEQUE(deletion)
        3.DISPLAY
        4.EXIT

1

 Enter element into the Queue: 2


 Enter the choice that you need
        1.ENQUE(insertion)
        2.DEQUE(deletion)
        3.DISPLAY
        4.EXIT

1

 Enter element into the Queue: 3


 Enter the choice that you need
        1.ENQUE(insertion)
        2.DEQUE(deletion)
        3.DISPLAY
        4.EXIT

1

 Enter element into the Queue: 4


 Enter the choice that you need
        1.ENQUE(insertion)
        2.DEQUE(deletion)
        3.DISPLAY
        4.EXIT

3

        1
        2
        3
        4



 Enter the choice that you need
        1.ENQUE(insertion)
        2.DEQUE(deletion)
        3.DISPLAY
        4.EXIT

2

 Deleted element is 1


 Enter the choice that you need
        1.ENQUE(insertion)
        2.DEQUE(deletion)
        3.DISPLAY
        4.EXIT

3

        2
        3
        4



 Enter the choice that you need
        1.ENQUE(insertion)
        2.DEQUE(deletion)
        3.DISPLAY
        4.EXIT

2

 Deleted element is 2


 Enter the choice that you need
        1.ENQUE(insertion)
        2.DEQUE(deletion)
        3.DISPLAY
        4.EXIT

1

 Enter element into the Queue: 1


 Enter the choice that you need
        1.ENQUE(insertion)
        2.DEQUE(deletion)
        3.DISPLAY
        4.EXIT

1

 Enter element into the Queue: 2


 Enter the choice that you need
        1.ENQUE(insertion)
        2.DEQUE(deletion)
        3.DISPLAY
        4.EXIT

3

        3
        4
        1
        2