Introduction of work
It 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, but again easy for a human.
The term "CAPTCHA" is an acronym based on the word "capture" and standing for "Completely Automated Public Turing test to tell Computers and Humans Apart".