DuckCorp Dico

Found one definition

1.                 From The Free On-line Dictionary of Computing (19 January 2023):
                   
   
   
                   
                     
   CSO
      Campus Phone Book software developed for, and originally used
      at, the Computer Services Office of the University of Illinois
      at Urbana-Champaign.  The server software is known as "qi" and
      the client is "ph".  Recent versions of the software refer to
      CCSO (Computing & Communications Service Office).
      (ftp://uxc.cso.uiuc.edu/).