Meaning of captcha by Jimeno Álvarez

CAPTCHA or CAPTCHA stands for Completely Automated Public Turing test to tell Computers and Humans Apart (Turing test public and automatically to differentiate human ) and machines. This test is controlled by a machine, rather than by a human as in the Turing test, for it consists of a reverse Turing test.This is a test challenge-response used in computing to determine when the user is or not human. The term was first used in 2000 by Luis von Ahn, Manuel Blum and Nicholas J. Hopper of the University Carnegie Mellon, and John Langford of IBM. It consists of the user to correctly enter a set of characters that are displayed in a distorted image that appears on the screen. Assumes that a machine is not able to understand and enter the sequence correctly so that only the human could do it.