Plugins options questions

Hi all,
i’m building a new plugin and i’ve also created an admin page to easily set its options.
Options are stored as an array in a single row in wp_options table.
I’m checked two “strange” issues with checkboxes:

1)if the checkboxes is uncheked the example pair
[plugname_option] => 1
is removed from the array instead of being given value “0” like
[plugname_option] => 0

2)checkboxes value are inserted as strings and not as integers into the DB so i have:
s:15:”plugname_option”;s:1:”1″

The checkbox code is like the following:
<input type=”checkbox” name=”plug_options[plugname_option]” value=”1″ <?php check_option(‘plugname_option’); ?>/>

Thanks in advance for your replies.