Question

What is CAPTCHA? And what is it specialties?

Answer 1

CAPTCHA means Completely Automated Public Turing test to tell Computers and Humans Apart.

In CAPTCHA, users have to find and type the letters which might be a combination of alphabets and numericals in a distorted image. This test will be validated by a computer which was administered by a human. This test is mainly to find whether the user is a human or a bot (a computer program which is able to click buttons and fill the blanks which can be done easily by some programs). So to prevent bot programs to increase traffic we use captcha to make sure that the user is a human.

Specialities of CAPTCHA:

Clearly it is a fully automated system. Once the program is done there will not be any need of human interference in the captcha system.

So it requires less human maintenance and thus will be producing more benefits in cost and reliability.

It might contain only numericals or only alphabets or a mixture of numericals and alphabets.

But they can be easily found by the programs to detect the alphabets and numericals.

So recently people are using image captcha which will ask for semantics to detect.

For example:

It will give an image with grids and will be asking to click the images with cars which a computer cannot find. Only a human can detect the car in any direction. And also it might ask to click all the grids containing traffic lights. These are just the examples. You can create captcha of any kind.

Hope you understood what is CAPTCHA and its types and some specialities with some examples.