function add_meta_box does not exist

hello,
today while going to make a plugin, I found this problem. after trying a lot i see that add_meta_box() function shows it does not exist.

here is the code I run to test availability:
if(function_exists(‘add_meta_box’)) {
echo ‘This function is available’;
} else {
echo ‘This function is not available’;
}

Output:
This function is not available

I get same thing on 2.7 and 2.6.2. but I can easily see that the function is available in template.php file. even my editor (eclipse) can jump to the function when I click.

how can I solve it? i need to add an extra box in post created/edit area.