CodeIgniter Library Management Project Shows 404 Page Not Found Error on localhost

In CodeIgniter, I want to add new student form but 404 page not found error occurs.I have tried many solutions but I failed.I am a newbie.Help me, please.

defined('BASEPATH') OR exit('No direct script access allowed');

class Student extends CI_Controller {

    public function __construct(){
        $data = array();

    public function Addstudent(){
        $data['title'] = 'Add New Student';
        $data['header']= $this->load->view('inc/header', $data, TRUE);
        $data['sidebar']= $this->load->view('inc/sidebar','', TRUE);
        $data['studentadd']= $this->load->view('inc/studentadd','', TRUE);
        $data['footer']= $this->load->view('inc/footer','', TRUE);
        $this->load->view('addstudent', $data);

Moreover, I have also remove index.php through .htaccess. Add helper classes.Configure Base_Url. Can anyone help me to solve this problem?I am using CodeIgniter 3.1.7.