A CAPTCHA (an acronym for “completely automated public Turing test to tell computers and humans apart”, trademarked by Carnegie Mellon University) is a type of challenge-response test used in computing to determine whether or not the user is human.

In this instance we are using this challenge response specifically in order to prevent comment spam which has been a continual irritation since I began to blog.

If you would like to read more about CAPTCHA you could:

• investigate Wikipedia’s page on the subject here: Wikipedia CAPTCHA;
• investigate the Wordpress Plugin created by Boriel that we use for our CAPTCHA here: Capcha! Plugin;
• alternatively check out the PHP class that the plugin is based upon here: PHP Class: HN CAPTCHA.