Is there a user manual and a theory manual for SACS that would help me better understand its functions and analysis results?

Regarding SACS, is there a user manual? And a theory manual? When I try to enter some values into SACS, I always wonder what the command and function mean. For example, what is the definition of Effective Length?, K Factor?, and Stream wave order? Could you let me know where I can obtain those documents I need?