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\noindent This is an almost-final draft of the \TeX\ program listing
that will be published someday in {\sl Computers and Typesetting},
Volume~1. I hope that a few brave readers will be able to help me improve
this material before publication, hence I am happy that Addison-Wesley
is making this preprint available.

A reward of \$1.28 will cheerfully be paid to the first person who finds
any typographic error in this document. Furthermore, suggestions for
improving the quality of the exposition are worth 32\rlap/c---provided,
of course that I agree with the suggestions. I'm particularly interested
in ideas for improving the quality of the index.

I believe that the final bug in \TeX\ was discovered and removed
on November~25, 1984. But if, somehow, an error still lurks in the code,
I~shall gladly pay a finder's fee of \$10.24 to the first person who
discovers it.  \ (This is twice the previous amount, and I plan to double
it again in a year; you see, I really am confident!)

Readers of this program will probably find one or two other publications
helpful: My paper ``Literate Programming'' in {\sl The Computer Journal\/
\bf 27} (1984), 97--111, is an introduction to the {\tt WEB} language in
which the program is written. Complete documentation of {\tt WEB} is
available as Stanford Computer Science report 980, ``The {\tt WEB}
System of Structured Documentation,'' (September 1983), 206~pp. Another
Stanford technical report, entitled ``A torture test for \TeX,'' establishes
criteria for programs that claim to be correct implementations of \TeX.
Order forms for these reports can be found at the back of each issue
of {\sl TUGboat}. \ (See Appendix~J of {\sl The \TeX book\/} for information
about TUG and about {\sl TUGboat}.)

Since I have learned much in the past from reading other people's programs,
I have tried to make my own program sufficiently stimulating that it
might give a bit of pleasure to its readers. There aren't many jokes, but
many of the algorithms are amusing and/or amazing.

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\rightline{--- D. E. Knuth, December 1984}
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`\TeX' is a trademark of the American Mathematical Society.

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The preparation of this report was supported in part by the National Science
Foundation under grants IST-8201926 and MCS-8300984,
and by the System Development Foundation.

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