How Can i Insert data In DataBase

In this Project For inserting Data in database cretaed  basically 3 pages. i m using Wamp Server ..My dataBase Name is "artipick" , table name ="user" and in table 4 Field name  id , username , password , email  .When i will Submit the form Its generate Error..

Plz Reply me..
1)controllers/Register.php
<?php
defined('BASEPATH') OR exit('No direct script access allowed');

class Register extends CI_Controller {

public function _construct()
{
parent ::_construct();
$this->load->model(array('mod_user'));
}

You've missed one underscore in constructor name. It should be __construct()