Circular Queue

#include <iostream>
#include <stdlib.h>
#define maks 5
using namespace std;

struct antrian{
    int f=-1;
    int r=-1;
    char data[maks];
}ant;

bool isempty(){
    if (ant.f ==  -1)
    {
        return true;
    }else{
        return false;
    }
}

bool isfull(){
    if(((ant.r+1) % maks) == ant.f)
    {
        return true;
    }else{
        return false;
    }
}

void enqueue(char data){
    if(isfull()){
        cout << "Antrian Penuh.." << endl;
        system("pause");
    }else{
        if(isempty()){
            ant.f = ant.f + 1;
            ant.r = ant.r + 1;
        }else{
            ant.r = (ant.r + 1) % maks;
        }
        ant.data[ant.r] = data;
        cout << "Data telah dimasukkan" << endl;
    }
}

void dequeue(){
    char data;
    if(isempty()){
        cout << "Antrian kosong" << endl;
        system("pause");
    }else{
        data = ant.data[ant.f];
        cout << "Data " << data << " telah di hapus" << endl;
        if(ant.f == ant.r){
            ant.f = - 1;
            ant.r = - 1;
        }else{
            ant.f = (ant.f + 1) % maks;
        }
    }
}

void display(){
    int i;
    if(!isempty()){
        if(ant.f > ant.r){
            for(i=ant.f;i<maks;i++){
                cout << "["  << ant.data[i] << "]" << " ";
            }
            for(i=0;i<=ant.r;i++){
                cout << "["  << ant.data[i] << "]" << " ";
            }
        }else{
            for(i=ant.f;i<=ant.r;i++){
                cout << "["  << ant.data[i] << "]" << " ";
            }
        }
    }
}

int main(){
    char data;
    int menu;

    do{
        system("cls");
        cout << "Front : " << ant.f << endl;
        cout << "Rear : " << ant.r << endl;
        cout << "Isempty ? "<< isempty() <<endl;
        cout << "Isfull ? " << isfull() <<endl;
        cout << "maks ? " << maks <<endl;

        display();
        cout << endl;
        cout << "Menu: "<<endl;
        cout << "1. Tambah(push)"<<endl;
        cout << "2. Hapus(POP)"<<endl;
        cout << "3. Keluar"<<endl;
        cout << "Masukkan menu: ";
        cin >> menu;

        if(menu == 1){
            cout << "Masukkan data : ";
            cin >>data;
            enqueue(data);
        }else{
            dequeue();
        }
    }while(menu != 3);


}