Why TeX?

[mcdonald at uxe.cso.uiuc.edu]

>> With TeX and its companion font generator, Metafont, you
>> can typeset just about any document.

>What does Tex do about dumb (non-bitmapped) output devices, like letter-
>quality printers? Everything I've heard about it makes it sound like a
>great deal if you have a laser-printer, but useless for a dumb output
>device. What's the story?

What does TeX do about non-bitmapped things like letter-quality printers?
Simple. It ignores them.

It can be used with high quality dot matrix printers, but as it must
use graphics mode, it will be slowwwwwww.

TeX was designed to make actual books, on actual typesetters. It is
a general purpose program for that purpose, but also contains
a large amount of stuff for doing mathematical typesetting.
Also, mechanisms for generating and properly placing tables, figures,
tables of contents, footnotes, endnotes, and references.
"Normally" it uses a special set of fonts, designed by (for?) Donald
Knuth and extended a bit for Latex by Leslie Lamport. These are
stored as bitmaps and downloaded to the printer. For printers,
such as actual typesetters and Postscript devices, that have suitable
internal characters (at least for text, as TeX really needs its own
very special stuff for math) one can provide it tables that describe
the size of characters, and devise special printer drivers to use these
characters. As far as I know, this is common only for Postscript.
   The TeX fonts, known generically as Computer Modern, contain
Roman-ish and sans-serif fonts in sizes from 5 point to 17 point.
Each size has different shape characters (i.e. the letter "a" in 
10 point Roman is not the same shape as 5 point blown up by a 
factor of two.) There are also bold, italic, and bold italic versions,
plus a special "math italic" it uses for setting math. And numerous
(very numerous) special math symbols. These fonts are available
for just about any type printer from 100 dot per inch to 5000 d.p.i.
And you can tell it to use, for example, 600 d.p.i. fonts on a 300
d.p.i. device, and get output twice as big (the intent being that
photoreduction would give output the same shape as real 300 d.p.i.,
but higher quality.)
    Finally, for those totally unfamiliar with it, TeX is a computer
language, not a word processor. It is fair to say that you "program"
your book.