Hi,
While making up a registration to fill a form i just come to know that there is a entry miss out by me and it was displaying it that what is the Captcha. But i didn't able to understand that what is the meaning of Captcha and where to find out and how to fill up the Captcha. It's very urgent for me to fill up the Captcha to complete the registration as well. Please help me out tof fill up my registration as early as possible, otherwise i will miss out the last date as well.

A Captcha is a type of challenge-response test used in computing as an attempt to ensure that the response is generated by a human being. The process usually involves a computer asking a user to complete a simple test which the computer is able to grade. These tests are designed to be easy for a computer to generate but difficult for a computer to solve. If a correct solution is received, it can be presumed to have been entered by a human. A common type of CAPTCHA requires the user to type letters and/or digits from a distorted image that appears on the screen.

The term "CAPTCHA" was coined in 2000 by Luis von Ahn, Manuel Blum, Nicholas J. Hopper, and John Langford (all of Carnegie Mellon University). It is an acronym based on the word "capture" and standing for "Completely Automated Public Turing test to tell Computers and Humans Apart". Carnegie Mellon University attempted to trademark the term, but the trademark application was abandoned on 21 April 2008.

A CAPTCHA is sometimes described as a reverse Turing test, because it is administered by a machine and targeted at a human, in contrast to the standard Turing test that is typically administered by a human and targeted at a machine.

The definition of CAPTCHA is "Completely Automated Public Turing Test To Tell Computers and Humans Apart.