TeX82 is a document compiler that does a good job of typesetting complex mathematical formulas. The definitive guide to TeX82 is a book entitled The TeXbook, written by the TeX's creator, Prof. Donald E. Knuth of Stanford University. Michael Plass and Lyle Ramshaw ported TeX82 from Pascal to Cedar, building on Edward McCreight's PasMesa, a Pascal-to-Mesa translator. This note describes how to run the Cedar incarnation of TeX.

When you do a Bringover of TeX, you will get the following files:

In addition, you will get an auxiliary DF file named TexWeb.df. This file describes all of the files that are distributed as part of the release of TeX from Stanford, and where to find them on our file servers. If you would like to see exactly what is available, look at the file named ``-read-.me'', described in TexWeb.df. I will just mention here a few files that might be intriguing:

Once you have loaded TeX, you will have access to three new commands: TeX, IniTeX, and InterruptTeX. The third is the easiest to explain, so we shall discuss it first. If TeX is in the middle of a long job, you can stop TeX dead in its tracks by clicking the ``STOP!'' button at the top of the CommandTool. But you might want to examine TeX's internal state, or you might want to make TeX pause in such a way that it could pick up again later. To do these things, get yourself another CommandTool (by clicking the ``Cmd'' button at the top of the screen) and execute the command ``InterruptTeX'' there. This will notify TeX that you would like it to pause and ask you for instructions at the next convenient opportunity.

By the way, TeX can only work on one job at a time, since it stores lots of information in its global frames. Suppose that you have one CommandTool, in which you have asked TeX to typeset a file. If you get yourself another CommandTool and ask TeX to start work on a second file while it is still chewing on the first one, the second request will just sit and wait until the first run is complete.

In order to understand the difference between the other two commands that TeX provides, we should discuss what happens on a standard timesharing machine. Such machines usually come with three versions of TeX. First, there is IniTeX, the most powerful of the three. IniTeX can read the ``pool'' file in order to initialize TeX's string-handling mechanisms; it can also take a set of hyphenation patterns and crunch them down into a compact data structure that can be searched at high speed; in general, it can build up a TeX world from scratch. The production version of TeX is named VirTeX. VirTeX can't do the initializations that IniTeX can, but, in compensation, VirTeX often has more memory capacity. VirTeX initializes itself by reading in a format file, with extension ``.fmt'', a snapshot of TeX's tables that IniTeX produces. In you take a VirTeX, load in the format file ``plain.fmt'', and then save the result away so that it can be reloaded rapidly, the result is the standard TeX.

In Cedar, the situation is somewhat different. The Cedar architecture has no provision for saving a program away with its tables initialized so that it can be loaded again rapidly (other than taking a Checkpoint, which is rather drastic). In addition, having code around that never gets executed is not very expensive in Cedar. As a result, there is only one TeX in Cedar rather than three, and it has all the power of IniTeX. But there are two different commands for invoking this one TeX, because TeX and IniTeX behave differently on startup. If you say ``TeX story'', TeX will initialize itself with your default format and then input the file ``story.tex''. If you say ``IniTeX story'', TeX will assume that ``story.tex'' is a macro file intended to produce a new format from scratch, and it will start reading it in without reading a format file first. Once the Cedar TeX is off and running, it behaves like an IniTeX no matter how you invoked it; that is, it is able to perform both ``\dump'' (which writes a format file) and ``\patterns'' (which builds a hyphenation trie).

One closing word about the capacities of things: I have set the various limits of the Cedar TeX on memory size, number of fonts, and the like to be at least as high as the current limits of TeX on TOPS-20 and TeX on VMS. Many of these limits could be expanded still further without much work by having a wizard recompile TeX.

TeX looks for four parameters in your user profile.

It is Don Knuth's official policy that source files for TeX be written in the ASCII character set or, if an extended character set is desirable, in a particular extended character set described in Appendix C of The TeXbook. We shall call this latter character set ``the TeX character set''; it was developed at MIT. The TeX character set is a strict superset of ASCII.

Most fonts at Xerox use a slightly different character set, which we shall call the Xerox character set. Sad to say, the Xerox set is not a strict superset of ASCII. In particular, there are conflicts concerning the character code values 136 (octal) and 137 (octal). In the Xerox character set, 136 is an up-arrow and 137 is a left-arrow. In ASCII, 136 is a circumflex and 137 is an underline. This discrepancy is an unfortunate thing; but we have to live with it. For all of the other printing character codes (from 040 through 176), the Xerox and ASCII systems agree.

I shall propose one way to handle this character set problem, based on the files TeX.style and TeX.tip. Other policies are possible, but I recomend that you read the following to understand the rationale behind my scheme before rushing out to design your own more wonderful scheme.

First, I propose that TeX in Cedar shall assume that its input files are given in the TeX character set, in accord with Knuth's policy mentioned above. This will dramatically improve the possibilities for shipping TeX source files between our machines and computers elsewhere and having everything work correctly. In order to avoid confusion about the characters associated with the codes 136 and 137, TeX source files should always be examined in a font with the correct character code mapping. There are currently two such fonts available: LPT, an MIT lineprinter font, and AMTEX, distributed with the TeX release. Both of these fonts are fixed-width fonts, I'm sorry to say. It would be relatively easy to produce a variable-width font with the correct character set for use on the screen; but getting such a font at printer resolution and installing it on printers would be much more work. I recommend that people look at TeX sources in the AMTEX font, which is what will happen if you apply TeX.style to your source files.

What about the codes 136 and 137? Well, no matter what you are typing, a TeX source file or anything else, you type the code value 137 by pushing the key with the two arrows on it and you type the code value 136 by pushing that key with the shift key held down. If you are typing to a file in the Xerox character set, the characters that appear will look like the arrows on the keytop. If you are typing a TeX source file in TeX.style, you will see an underline instead of a left-arrow and a circumflex instead of an up-arrow. Life is hard. Note that Plain TeX sets things up so that underline is a valid subscript character and circumflex is a valid superscript character. Thus, you can type subscripts and superscripts in one keystroke; they just look funnyjust as funny as in The TeXbook.

Left single quote is something of a problem. This character is assigned the code 140 (octal) in both the Xerox and the ASCII character mappings. But most people don't bother to use left single quotes when typing in Tioga, because there is no easy way to type one. The Tioga command SingleQuoteBrackets will surround the current selection by putting a left single quote on the left and a right single quote on the right. Thus, if the current selection is just the insertion caret, you can type a left single quote in two keystrokes as follows: first type <control><quote> to bracket the caret in single quotes; then type <shift><backspace> to delete the right single quote. But this is sort of a pain. I find that it is more convenient to be able to type a left single quote in one keystroke. This can be achieved by layering a new TIP table on top of the default TIP table. In TeX.tip, I suggest changing the behavior of the quote key as follows:

You may have other ideas about how to handle the problem of left single quote. If so, more power to you. But remember that you don't want to interfere with existing Tioga commands that you will want at other times. Also, there is substantial benefit to be had from keeping your user interface as simple, as consistent, and as much like everyone else's as possible.

A few comments about mechanics: TIP table specifications are pretty easy to write, and TeX.tip is a good example of how to do simple things. In order to layer TeX.tip on top of the default TIP table in your Cedar world, you must edit your user profile to say ``TiogaTIP: TeX.tip Default''. Then, you must invoke the command ``ReadTiogaTipTables'' in order to make the change take effect.

You have your choice about whether to use only ASCII or the extended TeX character set in your source files. The former choice improves portability to other TeX installations, while the latter is more convenient here. The extended character set includes various useful characters. It includes an up-arrow and a down-arrow at 013 (=^K) and 001 (=^A) respectively. Plain TeX sets things up so that these also act as a superscript and a subscript character; and they look better in your source files. There are only two problems with using them: first, they are not in standard ASCII, so you are hurting your portability; second, they are hard to type. You can type them in two keystrokes by typing {<K>; <control><K>} or {<A>; <control><K>}, but two keystrokes is a lot worse than one. You could change your TIP table so that they could be typed in one keystroke; but the problem then is what keytop to assign them to. Our keyboards are already pretty loaded, and most reasonable combinations of keys already mean something useful. Pushing the <arrows> key by itself gives 137, which you certainly need for Cedar programs even if you didn't want it for TeX; <shift><arrows> gives 136, also used in Cedar; and <control><arrows> and <shift><control><arrows> are useful for reading and writing the format of a Tioga node.

There are other extended characters that you might enjoy. I am particularly fond of the characters for not-equals, less-than-or-equals, and greater-than-or-equals. My suggested TIP table TeX.tip sets things up so that these characters can be typed by typing <control><equals>, <control><comma>, and <control><period> respectively. You might enjoy using these characters, or you might want to change your TIP table to get at different extended character codes in one keystroke.

Xerox fonts do not follow the magnification scheme that the AMR fonts do. If you want to typeset something in TimesRoman10, for example, you should ask for ``\font\tr=timesroman at 10truebp''. The name after the equals sign is the file name of the TeX font metric file. You can find out what TeX font metric files exist by listing the appropriate directory. Note that one metric file describes all sizes of TimesRoman, since the characters in TimesRoman just scale photographically to become different sizes. You should specify the size that you want by giving an ``at'' clause. And you should use ``truebp'' as the unit; ``true'' to prevent magnification from having effect, and ``bp'' because Xerox fonts are sized in ``big points'' rather than TeX ``pt'' small points. Be aware that Xerox fonts tend to run large; you have to magnify AMR10 by a half-step in order to make it look about the same size as TimesRoman10.

There are various more devious ways of trying to address the problem raised by character codes 136 and 137. For example, one might make up a font that was like AMTEX in every way except that 136 and 137 came out as arrows. Or even hackier still: it is rumored to be possible to call an arbitrary Cedar procedure from a TIP table. Hence, it might be possible to layer a TIP table on top of Default in which depressing the <arrows> key caused a proc to run which would look at the file name of the file in the selected viewer to see if the extension was ``.tex'' or not, and do different things in the two cases. The mind boggles at the levels of confusion that might result from this type of hackery.

There is a separate memo called BuildingTeX.tioga, available through TeX.df, which describes how to compile the Cedar TeX, in case its limits should need to be expanded or in case conversion to a new release of Cedar should become necessary.