vulnerability

[hackit]

guys i just read a vulnerability in the calculator of windows. vulnerability is like this:

*) open calculator

*) type 4 and then take its square

*) then minus two from the result

shocked....

answer should be 0 but it shows a different answer..

please help me on this.

[jingda]

I suppose you are taking course in computer security? Correct me if I am wrong. So what do you want us to help you with?

[Reverend Jim]

First of all when you take the square of 4 you get 16. I presume you meant square root. I would imagine that the algorithm used to find the square root results in 2 plus a very very small fraction which is not shown because it is so much smaller than 2. When you subtract 2 from that you are just left with the fractional part which is, at least on my computer, around -8 times 10 to the -39th power which is damn close to zero.

One of the first demonstrations I had on how computers do math was back in 1971 when it was shown that 1/3 + 1/3 + 1/3 was actually slightly less than one according to the computer.