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I've removed the stuff comparing typical uses of systematic vs. non-systematic, for the following reasons:

• The terms "systematic" and "non-systematic" are typically used to describe channel coding, not source coding. Therefore, discussions of "redundancy within the original bit stream" are irrelevant.

• Any non-systematic block or convolutional code can be transformed into an equivalent systematic code, that performs identically. Therefore, the following claims are untrue:

• • "They are appropriate for noisy channels (e.g. wireless communication)." In fact, systematic codes are almost always used in practice, as they are far easier to generate and decode.

• • "Systematic codes are typically used when the probability of loss or damage is low or transmission latency is an issue." This implies that they are not generally used when the probability of loss is high.

• • "Systematic codes have a lower bound on the size of the encoded output: the size of the original message." This of course applies to non-systematic codes as well.

Oli Filth 22:54, 22 February 2007 (UTC)Reply

Please clarify description for non-systematic case: if x1 x2 x3 x4 is message and p1 p2 p3 is other bits of codeword will be some C generate encoded string, for example, p1, x4, p2, x1, x2, p3, x3 systematic code or not-systematic ?! " Conversely, in a non-systematic code the output DOES NOT CONTAIN the input symbols. " My example CONTAIN input symbols but in other, not solid, order. — Preceding unsigned comment added by 78.25.122.212 (talk) 18:00, 16 May 2015 (UTC)Reply

Yes, if x1 x2 x3 x4 is the message, and the encoded string always contains the message bits in some fixed location in each codeword such as, for example, p1, x4, p2, x1, x2, p3, x3, then yes, the encoding is a systematic code.

It doesn't matter if those message bits are in the same order.

It doesn't matter if the message bits are consecutive in the codeword or if they are somehow interleaved with the "parity" bits.

I find trivial secret sharing a nice example of a non-systematic code.

How can we improve this article to make this more clear? --DavidCary (talk) 02:40, 21 October 2025 (UTC)Reply