Captcha:
-------------

In many registration forms to complete registration

process,we find a figured letters which should be typped by

seeing with naked eye and which cannot be coppied.

Not only in registration forms but also during

passsword recovery we find this.Which is called as CAPTCHA

Why?and for what purpose it is used?

CAPTCHA(Completely Automated Public Turing Test To Tell

Computers and Humans Apart)is a test used in computing to say

that the response is not generated by any computerised tool.

Why is Captcha used?

Many companies provide free e mail services.To abort the

success of such organizations there is a chance for other

organization to mis-use those email services by using some

computerised tools. For example there is a registration form

which has no of fields to be entered.There are some tools which

can enter the values into fields simultaneously, and can create

lakhs of emails with in very few minutes,this will abort from

creating new emails for the other users.

Solution for this problem:

The solution to this problem was to use CAPTCHAs to

ensure that only humans obtain free accounts. In general, free

services should be protected with a CAPTCHA in order to prevent

abuse by automated scripts.