# TeX distribution and TeX implementation

TeX distributions are the large collections of TeX-related software to be downloaded and installed. For example, Tex Live and MiKTeX.

TeX implementations are for example

Web2c is the name of a TeX implementation, originally for Unix, but now also running under DOS, Amiga, and other operating systems. By TeX implementation, we mean all of the standard programs developed by the Stanford TeX project directed by Donald E. Knuth: Metafont, DVItype, GFtoDVI, BibTeX, Tangle, etc., as well as TeX itself. Other programs are also included: DVIcopy, written by Peter Breitenlohner, MetaPost and its utilities (derived from Metafont), by John Hobby, etc.

1. So I wonder what differences and relations are between Tex distributions and Tex implementations?
2. If Web2c is not a TeX distribution, then why?
3. What else besides Web2c are also examples of TeX implementations?

Thanks!

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Web2C is a method for going from the "written program" to the compiled binaries for a specific platform: it transforms the Pascal sources into C sources which can then be compiled with a C compiler. A TeX distribution contains also all the necessary files to run various flavors of TeX (Plain, LaTeX, ConTeXt, …). –  egreg Jul 21 '12 at 10:35
@egreg: (1) I still don't see why Web2C is not a distribution. (2) Is Web2C an engine/compiler/interpreter then? –  Tim Jul 21 '12 at 12:14
Web2C is properly a set of programs that transform a WEB source (literate programs written in Pascal) to C for later compilation. –  egreg Jul 21 '12 at 12:43

Web2C is a method for going from the "written program" to the compiled binaries for a specific platform: it's a set of script that transform the Pascal sources (from the WEB file after applying tangle) into C sources which can then be compiled with a C compiler.
A TeX distribution contains also all the necessary files to run various flavors of TeX (Plain, LaTeX, ConTeXt, …): base files such as plain.tex or latex.ltx, font metric files, support files, other scripts and so on.