whats wrong with my code?

i get the error
Assets/Scripts/CursorGone.cs(12,9): error CS0246: The type or namespace name `function’ could not be found. Are you missing a using directive or an assembly reference?
and it higlights the function update.

using UnityEngine;
using System.Collections;

public class CursorGone : MonoBehaviour 
{

	function Start ()
	{
		Screen.showCursor = false;
	}
	
	function Update () 
	{
		if (Input.GetKey (KeyCode.Tab))
		{
			Screen.lockCursor = false;
			Screen.showCursor = false;
		}   
		else
		{
			Screen.lockCursor = true; 
			Screen.showCursor = true;
		}
	}
}

function Start ()
{
Screen.lockCursor = false;
}

function Update ()
{
    if (Input.GetKeyDown (KeyCode.Tab))
    {
        if(Screen.lockCursor == true)
        {
            Screen.lockCursor = false;
        }
        else
        {
            Screen.lockCursor = true;
        }
    }
}

Try this. also, Screen.lockCursor also hides the mouse so you dont need Screen.showCursor