The default qualifiers for the STEP command are the default
    qualifiers last established by the SET STEP command. If you did
    not enter a SET STEP command, the default qualifiers are /LINE,
    /OVER, /NOSILENT, and /SOURCE.

    Enabling screen mode by pressing PF1-PF3 enters the SET STEP
    NOSOURCE command as well as the SET MODE SCREEN command (to
    eliminate redundant source display in output and DO displays).
    In that case, the default qualifiers are /LINE, /OVER, /NOSILENT,
    and /NOSOURCE.

    Related commands:

       STEP
       SET STEP