What is the minimum TeX one can use to put together a mathematical document?

Question

Being a mathematician, I use LaTeX a lot for writing. However, I am interested (mildly) in working with TeX instead, even if only for keeping my own notes. What is the minimum amount of TeX do I need to know to produce reasonable documents with mathematical content? I'm not interested in the finer points of compositing and typefaces and so on, so I may be barking up the wrong tree here.

Also (and this is a stretch) what about diagrams in TeX? Usually I use xymatrix in LaTeX, is there an easy way to do simple diagrams in TeX?

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Edit: The answers to the second question are good, but what about the first? Shall I go back a step and ask:

What is the minimum amount of TeX do I need to know to produce reasonable documents?

Answer 1

For graphics, TikZ supports TeX, LaTeX and ConTeXt. The beautifully illustrated manual starts off with several tutorials that show how to set TikZ up for use with TeX, LaTeX or ConTeXt. After the environment has been set up, the syntax used to draw pictures is consistent across all three systems.

MetaPost is another vector drawing language that grew out of MetaFont and inspired much of the syntax used by TikZ. Hans Hagen, the creator of ConTeXt, has done a lot of work on MetaPost and has produced a very fine manual detailing the system and his MetaFun extensions. The University of Berkeley has an example that shows how to use MetaPost from plain TeX or AMSTeX.

LuaTeX has MetaPost support baked in thanks to MPLib. A plain-TeX example for using MetaPost code inside LuaTeX can be found here.

Answer 2

On the first question you should be more elaborate. At the most minimum level, the only TeX command you need to know is \end. You should explain what you want to do, reasonable documents on its own is just too vague to give better answers.

On the subject of learning tex, see the excellent (and nowadays free) book TeX by Topic by Victor Eijkhout.

For a short introduction to (plain) TeX, try A Gentle Introduction to TeX by Michael Doob. It is quite old and the part about running TeX and editing is somewhat obsolete, but it covers enough of the plain functionality to get started, and it very easy to follow.

Answer 3

I use plain ol' TeX all the time when I want to do something fast. Sometimes from the command prompt. As has been pointed out, the minimal command is \bye. e.g.

$ e^{i\pi} + 1 = 0 $
\bye

So, the answer to your first question is: you need to know commands in TeX's math mode (mostly the same as LaTeX) and the command \bye . You should be able to make all the notes you need with that.

Answer 4

AMSTeX works with plain TeX, adding features for mathematics. It also provides simple macros for (commutative) diagrams: \CD ... \endCD.

Answer 5

You can use plain TeX for mathematics. (My PhD thesis, written two decades ago, was typeset in plain TeX with additional macros.) Of course, you may have to provide a number of additional macros if you want cross-referencing,...

As for diagrams, XY-pic (which is what I think you mean by xymatrix) works just fine in plain TeX; although I have not used it in plain TeX in years.