A CAPTCHA or Captcha (pronounced )is a type of challenge-response test used in computing to ensure that the response is not generated by a computer. The process usually involves one computer (a server) asking a user to complete a simple test which the computer is able to generate and grade. Because other computers are unable to solve the CAPTCHA, any user entering a correct solution is presumed to be human. Thus, it is sometimes described as a reverse Turing test, because it is administered by a machine and targeted to a human, in contrast to the standard Turing test that is typically administered by a human and targeted to a machine. A common type of CAPTCHA requires that the user type letters or digits from a distorted image that appears on the screen.
The term "CAPTCHA" (based upon the word ) was coined in 2000 by Luis von Ahn, Manuel Blum, Nicholas J. Hopper (all of Carnegie Mellon University), and John Langford (then of IBM). It is a contrived acronymfor"Completely Automated Public Turing test to tell Computers and Humans Apart."Carnegie Mellon University attempted to trademark the term,[2] but the trademark application was abandoned on 21 April 2008.[3] Currently, CAPTCHA creators recommend use of reCAPTCHA as the official implementation.[4]
and both of your captchas are blowing my theory of how captchas are generated. told ya. now i get this one:preck
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