When you sign up something like a free e - mail account, you may be presented with a CAPTCHA. the most common form of CAPTCHA s an image of several distorted letters. CAPTCHA stands for:
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"Coverage Analysis and Planning Tool for Computers and Humans Apart."
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"Completely Automated Public Turing test to tell Computers and Humans Apart"
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"Completely Applied Parallel Technologies for Communication and Hardware Apart".
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"Comparable Additional Protected Turing test to cell Computers and Humans Apart".