  3.  The GENESIS Script Language Interpreter

  The GENESIS Script Language Interpreter (SLI) provides a framework in
  which a simulation programmer can define and manipulate GENESIS
  elements.  The SLI interprets statements in the GENESIS simulation
  language, and constitutes the operating system ``shell'' at work when
  you are running GENESIS.

  The simulator shell is an interpretive operating environment which
  lets you:

  o  execute GENESIS routines (e.g., help, step, stop, openfile)

  o  execute operating system shell commands (e.g., ls, cat, vi)

  o  define variables (integer, floating point, or string types)

  o  evaluate arithmetic expressions

  o  invoke control structures such as conditionals and loops
     (if...then, while, for, or foreach loops)

  o  define and execute your own functions

  You can perform these operations in either of two ways:

  o  enter commands directly at the keyboard (the ``command line'')

  o  read commands from text files (``scripts'')

  User-defined SLI scripts are used to glue the pieces of a simulation
  together.  XODUS graphical objects that you use to define the front
  end of a simulation and GENESIS data handlers are all controlled from
  SLI scripts.

  The shell contains a library of basic commands which you can augment
  through the addition of compiled C commands or interpreted SLI
  functions.
