Sdraw is used to draw cons cell diagrams, which is used in the book "Common LISP: A Gentle Introduction to Symbolic Computation" by Davi S. Touretzky.  To load it, first load sdraw.asd using load function, then use ASDF's (asdf:load-system (quote sdraw)) or Quicklisp's (ql:quickload (quote sdraw)).

Both ASDF(https://asdf.common-lisp.dev ) and Quicklisp(https://www.quicklisp.org/beta ) are free software.