Runtime Environment

Consider the following program:

int main()       int f1()          int f2(int X)              int f3()
{                {                 {                          {
   f1();           return(1);        f3();                      return(5);
   f2(2);        }                   if (X==1)                }
   f3();                               return f1();
   return(0);                        else
}                                      return (X*f2(X-1));
                                   }

Which one of the following options represents the activation tree corresponding to the main function? The four trees (A) to (D) are shown in the figure.

What will be the output of the following pseudo-code when parameters are passed by reference and dynamic scoping is assumed?

a=3;
void n(x) {x = x * a; print(x);}
void m(y) {a = 1; a = y - a; n(a); print(a);}
void main() {m(a);}

Consider the program given below, in a block-structured pseudo-language with lexical scoping and nesting of procedures permitted.

Program main;
   Var ...

   Procedure A1;
      Var ...
      Call A2;
   End A1

   Procedure A2;
      Var ...

      Procedure A21;
         Var ...
         Call A1;
      End A21

      Call A21;
   End A2

   Call A1;
End main.

Consider the calling chain: Main → A1 → A2 → A21 → A1 The correct set of activation records along with their access links is given by