Heap allocation is required for languages.

Given the following Pascal like program segment:

Procedure A;

     x,y:intger;

     Procedure B;

            x,z:real;

            S1

     end B;

     Procedure C;

            i:integer;

            S2;

     end C;

end A;

The variables accessible in S1 and S2 are

Which of the following languages over $$\left\{ {a,b,c} \right\}$$ is accepted by Deterministic push down automata?

$$\sum { = \left\{ {a,b} \right\},\,\,} $$ which one of the following sets is not countable.