Implementation Of Circular Queue Using Arrays

Compiler used: Turbo C
Language C

#include<stdio.h>
#include<conio.h>
#include<stdlib.h>
void main(){
clrscr();
//queue deletion from front, insertion from rear
//check for overflow/underflow
int queue[10], front=-1, rear=-1, choice=0, entry=0, i;
while(choice!=4){
    printf("\nChoose from the following options:\nPress 1 to insert.\nPress 2 to delete.\nPress 3 to display.\nPress 4 to exit.\n\nYour choice is? ");
    scanf("%d",&choice);

    switch(choice){

        case 1:

        clrscr();
        if(rear==9 && front==0 || rear==front-1){
            printf("\nOverflow! Queue is full.\n");
        }
        else if(front==-1 && rear==-1){
            printf("\nPlease enter your number: ");
            scanf("%d",&entry);
            queue[++rear] = entry;
            front =0;
            printf("\nYour number has been entered!\n");
        }
        else{   printf("\nPlease enter your number: ");
            scanf("%d",&entry);
            ++rear;
            rear=rear%10;
            queue[rear]=entry;
            printf("\nYour number has been entered.\n");
        }
        break;

        case 2:
        clrscr();
        if(rear==-1){
        printf("\nUnderflow! Queue is empty.\n");
        }
        else if(front==rear){
        printf("\nThe number has been deleted!\n");
        front=-1;
        rear=-1;
        }
        else{
        front++;
        front = front%10;
        printf("\nThe number has been deleted from the queue!\n");
        }
        break;

        case 3:
        clrscr();
        if(rear==-1){
        printf("\nThe queue is empty.\n");
        }
        else if(front<=rear){
        for(i=front;i<=rear;i++){
        printf("%d ",queue[i]);
        }
        }
        else{
        for(i=front;i<=9;i++)
        printf("%d ", queue[i]);

        for(i=0;i<=rear;i++)
        printf("%d ", queue[i]);
        }
        break;

        case 4:
        exit(0);

        default:
        clrscr();
        printf("\nInvalid Choice!\n");
        break;

    }
}//end of while
}//end of main

PS: Many improvements are possible in the program. You are welcome to suggest them in comments! :)