Unassigned outputs in Process blocks

A common mistake in writing a combinational process is to leave an output unassigned.  If there is a path through the process in which an output is NOT assigned a value, then that value is unassigned.

ARCHITECTURE bad of majority is

begin

    process (A, B, C)

      begin

              if (((A = '1') and (B = '1')) or

                  ((A = '1') and (C = '1')) or

                  ((B = '1') and (C = '1')) ) then

                 Y <= '1';

              end if;

       end process;

end bad;

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