I kinda need help... if someone here is familiar with hamming code...

[glacial gust]

Its a 20 bits word(P1 is LSB)
10001111001111001001
we need to find the wrong bit, and replace it
(I have final solution but dont know how to get there)

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[minor fiber]

A Hamming code is an error-correcting code, right? So you need to identify the transmission bits and the correction bits.

[glacial gust]

yeah, but how do I find the wrong bit?

[minor fiber]

...by first identifying the transmission bits and the correction bits.

[glacial gust]

If Im not wrong the parity bits are 1,2,4,8,16

[minor fiber]

So then find the parity bit(s) which disagree with the parity of the relevant data.

[minor fiber]

@glacial gust

[glacial gust]

So how do I get to the wrong bit?

[minor fiber]

...by... checking which parity bits... disagree... with the parity... of the relevant... data.

[glacial gust]

The only parity bit that should be 1 is P16, the rest are 0.
So P1,P4,P8 are 'wrong'

[minor fiber]

And which bit do all of them cover?

That is, write the bit numbers in binary.

The wrong bit is the bit whose number in binary has 0 in the position of all the correct parity bits and 1 in the position of all the incorrect parity bits.

[glacial gust]

Ok, I think Im starting to get it.
Thank you!

[glacial gust]

well, I got it figured out, thank you!

[minor fiber]

You calculated p1 to be 0, but in the codeword it's 1. That makes it an incorrect parity digit, but you've recorded it as a 0 in the position of the flipped bit.

You misunderstood; the flipped bit is not the bit with the position equal to the number formed by the parity bits. You check the parity bits, place a 0 in that place value if the parity bit is correct, and place a 1 if the parity bit is incorrect.

You also included the parity bit itself in the calculation of the parity of the bit, which is not only incorrect, it's potentially paradoxical.

[glacial gust]

well now im confused, do you have any video or somthing that teach that?

[minor fiber]

Okay, stop. Go back to the beginning. Write out the received word and identify the parity bits.

[glacial gust]

like this?

[minor fiber]

Right. Now, which bits does P1 count the parity of?

[glacial gust]

all of the odd bits (not including him)

So its 5, then P1 should be 1

And because he is already 1 I put 0 in the first place of the correction code?

[minor fiber]

Correct.

Now, which bits does P2 count the parity of?

[glacial gust]

3 , 6,7 , 10,11 , 14,15 , 18,19 and that is 4-> P2 = 0, true -> C2 = 0

[minor fiber]

Okay, here's a chart from Wikipedia about how a Hamming code works:

It says that the parity bit does count itself, but that seems paradoxical to me.

@glacial gust For instance, what happens if the parity of the non-parity digits is 1? If the parity bit counts itself, then it's impossible to set correctly, because then if it's 1, then the whole set has a parity of 0, and if it's 0, then the whole set has a parity of 1.

Okay, wait, the parity bit takes whatever value is necessary to make the sum of all the bits it covers even. That makes sense.

And then the bit "covers" itself not because it counts the parity of itself but because if exactly one parity bit is wrong it indicates the corruption of that parity bit.

[glacial gust]

crazy how someone just envet this thing .....

[orchid wing]

@glacial gust

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