Index by category

Hello everyone, I fit my WordPress site design, I deal with WordPress long time but I ran into a small problem. Until now I used the code:
<? php $ catPost = get_posts (array (‘category’ => get_the_category_by_ID (1), ‘numberposts’ => 3)); ?>
To select a category from posts where posts are displayed, I copy the code and paste it that way all Israel is currently available. I want this time, instead of doing this, every time I open Sinhala News that will do this automatically (add Sinhala News new page index and copy the code did category specific) example will show where the article where the author in the category X 3 times, so it will do all categories . How to do it? : S
Thank assistants, Sagi.
* Sorry about my bad English