The two parts of this book contained the entire source listing

of the Unix Version 6 kernel, and a commentary on the

source discussing the algorithms. These were circulated

internally at the University of New South Wales beginning

1976-77, and were, for years after, the *only* detailed kernel

documentation available to anyone outside Bell Labs.

Because Western Electric wished to maintain trade secret

status on the kernel, the Lions book was never formally

published and was only supposed to be distributed to

affiliates of source licensees (it is still possible to get a

Bell Labs reprint of the book by sending a copy of a V6 sourcelicence to the right person at Bellcore, but *real* insiders

have the UNSW edition). In spite of this, it soon spread by

samizdat to a good many of the early Unix hackers.