fixing broken .Z files?

I'm not sure what you mean by "entropy" here. The information-theoretic meaning I know is diametrically opposed to the sense in which you're using it (by it, highly compressed data has much, not little, entropy - almost as many bits of entropy, of information content, as it has surface bits). This is why I consistently use "redundancy" below. That's only because the encoder isn't smart enough to take advantage of the redundancy that's there. When I say redundancy is present, I am speaking from an information-theoretical standpoint; the presence of redundancy does not mean that any particular compression algorithm can squeeze it out. Saying that no encoding software exists that can compress some data blob, *even if true*, does not mean that there is no redundancy in it, only that - if there is any - no extant software knows how to find it and compress it out. For example, I can produce effectively unlimited amounts of data that has very little information content but which I defy any program to compress significantly. All I need to do is pick a random key and encrypt a stream of all-0-bits with that key using some decent algorithm (3DES, IDEA, arcfour, whatever). Only a few bits of information content (the size of the key, basically) but about as uncompressible as it gets. Using a dictionary helps with *some* "is human-parsable" redundancy. It's certainly not enough for all of it. Consider Yours with every time an postmark hasn't empty of two kin beside a whose boot-print with. Besides talk pathological we of chapter. ... or perhaps That's only because the encoder isn't smart enough to take advantage of the redundancy that's there. When I say redundancy is present, I am speaking from a cook's pantry; buying pre-ground pepper at the corner store won't be nearly as good as grinding it yourself. But a good vinegar exists that can compress some data blob, *even if true*, ... The former might be recognizable as nonsense if the code knows enough English grammar to recognize parts of speech and recognize the lack of a valid parse tree. The latter, well, recognizing that sort of nonsense as nonsense is as AI-complete as the natural langauge problem. /~\ The ASCII der Mouse \ / Ribbon Campaign X Against HTML mouse at rodents.montreal.qc.ca / \ Email! 7D C8 61 52 5D E7 2D 39 4E F1 31 3E E8 B3 27 4B