Most people who navigate the internet certainly has been asked to confirm that it is not "robots" or as stated "bot" via Capcha system. Essentially the user must katharograpsei a text that appears random, often with distinct markings, incomprehensible writing and generally not visible form. The main reason is to combat spam messages from malicious programs that are trying in this way to gain access to email accounts and other services.

CAPTCHA: Εσείς ξέρετε πώς δουλεύετε για τη Google χωρίς να το γνωρίζετε;

Since 2009 it has implemented the Google digitizing old and rare documents and books with the purpose of placing the public through the Google Books Project. These texts are scanned and the scan is processed by special programs that convert the image into normal text with character recognition help. But conversion programs several times fail because of the scanning condition to convert it into text and there are many mistakes.

Image result for google captcha

Here comes Capcha to fill this gap. In Capcha displayed all illegible words and phrases from the scans and users are essential to decode them. Can a word seem unimportant but capcha forms filled daily is unthinkable number. Indicatively, in a few months, Internet users contribute to the digitization of documents 20 years of the New York Times, while in the first year were digitized over 17,000 books.