>I would like to know why the gnat sends the  message :
>  "type (Unit) must be declared abstract or Set (procedure) overrides"
>when I'm compiling the package body "Controller-p.adb";the error is detected
>in the specification, i.e., in "Controller-p.ads".

GNAT is right. you must override Set has you override Control. These
procedures are abstracts.

Set is not overrided in Controller.P. The Set in Controller.P has not the same
set of parameters (they are 2 differents procedures) :

In Controller :

   procedure Set     (Device      : in  out  Unit)  is abstract;

In Controller.P :

   procedure Set      (Device      :   in  out  Proportional_Controller;
                       Gain        :   in       Parameter);

Hope this helps,
Pascal.
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