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, release notes, 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
PV-API.txt
   Details about the PV API
Examples.txt
   Annotated example programs