Disclaimer: Quite a lot of the explanation text is copied from source code documentation by Hans Hagen. Always assume that the errors are mine and the good jokes are his.
The current text will mostly deal with the file [[source:syst-gen.
tex| syst-gen. tex]].
Most of those macros are very basic, and many of them are related to programming constructs like flow control (<code>\if</code> statements), data structures (comma separated lists), and definitions.