Queue Program

//  Queue Program
//  Date : 08.04.19
#include<iostream>
#include<cstdlib>
#define max_size 20
using namespace std;

class queue_class{
    int queue_array[max_size];
    int front_index, rear_index;
    void insert_queue();
    void delete_queue();
    void display();
public:
    queue_class(){ front_index = rear_index = 0; }
    void control_function();
};

void queue_class::control_function(){
    while(1){
        cout << "*****Welcome to Queue program*****\n"
             << "Press 1 to Insert.\n"
             << "Press 2 to Delete.\n"
             << "Press 3 to Display the Queue.\n"
             << "Press 4 to Exit.\n"
             << "Enter Your choice: ";
        int choice; cin >> choice;
        system("cls");

        if(choice == 1) insert_queue();
        else if(choice == 2) delete_queue();
        else if(choice == 3) display();
        else if(choice == 4) break;
        else cout << "Wrong Choice.\n\n";
    }
    return;
}

void queue_class::insert_queue(){
    if(rear_index == max_size){
        cout << "Queue Overflow\n";
        return;
    }
    else{
        cout << "Enter Element to insert: ";
        cin >> queue_array[rear_index++];
    }
}

void queue_class::delete_queue(){
    if(front_index == max_size || front_index == rear_index){
        cout << "Queue Underflow\n";
        return;
    }
    else{
        cout << "Element " << queue_array[front_index++]
             << " is deleted\n";
    }
}

void queue_class::display(){
    if(front_index == max_size || front_index == rear_index){
        cout << "Queue Underflow nothing to display!!!\n";
        return;
    }
    else{
        cout << "The elements in the Queue are: \n";
        for(int i = front_index; i < rear_index; i++){
            cout << queue_array[i] << ' ';
        }
        cout << endl;
    }
}

int main(){
    queue_class ob1;
    ob1.control_function();

    return 0;
}