Is Index file necessary in each website?

Is Index file necessary in each website? If yes, then how we can hide it from the from the web searcher?

 

Create robots.txt in your site root directory

robots.txt:
User-agent: *
Disallow: /

 

why hide it?
i don't get why you would hide the index when its your homepage.

 

But i think robots.txt used for the crawler and not for the user point of view.
How we can hide index file from user with robots.txt

 

For users - .htaccess

Order Allow,Deny
Deny From All

 

I don't want to remove my home page. I try to tell my question with an example.
Suppose a website open with 'abc.com' and its also open with 'abc.com/index.php' so now what can i do so the user not able to open /index.php and crawler also treated that index file as 'abc.com' and not consider it as the different page with duplicate content.

 

Redirect 301 /index.php /

Code (markup):

Or add this in your index.php:

if($_SERVER['REQUEST_URI']=='/index.php')header('Location: /');

PHP:

 

Thanks a lot..