DuckCorp Dico

Found one definition

1.                 From The Free On-line Dictionary of Computing (19 January 2023):
                   
   
   
                   
                     
   es
      1. <networking> The country code for Spain.
      2. <operating system> Extensible Shell.
      3. (Expert System) An expert system for the IBM PC
      featuring forward chaining, backward chaining and fuzzy
    set relations.
      (ftp://ftp.uu.net/pub/ai/expert-sys/summers.tar.Z).
      [BYTE Oct 1990].
      (1999-02-01)