You are looking at the EPICS State Notation Language compiler
and runtime sequencer.

For more information see the .txt files under documentation:

Introduction.txt
   What all this is about, licensing, and other trivia
Installation.txt
   How to download, build, etc
Tutorial.txt
   Gentle introduction to SNL, some (sloppy) semantics
Compiling.txt
   All about snc, the SNL compiler
Using.txt
   How to create a working SNL program
Reference.txt
   SNL syntax and built-in procedures
Examples.txt
   Annotated example programs
ReleaseNotes-2-0-and-older.txt
ReleaseNotes-2-1.txt
ReleaseNotes-2-2.txt
   Release notes
KnownProblems.txt
   What the name says
Plans.txt
   New features, ideas, and wishes

You can also view the documentation online at
http://www-csr.bessy.de/control/SoftDist/sequencer/