8. Consider the following Ada Skeletal program: Procedure Main is X: integer; Pr

Question

8. Consider the following Ada Skeletal program:

Procedure Main is

X: integer;

Procedure Sub3; -- This is a declaration of Sub3

                                    - -It allows sub1 to call it

Procedure Sub is

X : Interger;

Procedure Sub2 is

     begin - - of Sub2

. . .

end; - - of Sub2

begin - - of Sub1

. . .

end; - - of Sub1

Procedure Sub3 is

begin - - of Sub3

. . .

end;    - - of Sub3

begin   - - of Main

. . .

end; - - of Main

Assume that the execution of this program is in the following unit order :

Main calls Sub1

Sub1 calls Sub2

Sub2 calls Sub3

Assuming static scoping, in the following which declaration of X is the correct one for a reference to X?

Sub1

Sub2

Sub3

B. Repeat part a, but assume dynamic scoping.

9. Assume the following Ada program was compiled and executed using static-scoping rules. What value of X is printed in procedure Sub1?

Under dynamic-scoping rules, what value of X is printed in procedure Sub1?

Procedure Main is

X : Integer;

Procedure Sub1 is

Begin - - of Sub1

Put(X);

End; - - of Sub1

Procedure Sub2 is

X : Integer;

Begin - - of Sub2

X := 10;

Sub1

End; - - of Sub2

Begin - - of Main

X :=5;

Sub2 - - of Main

12. Consider the following C program:

Void fun(void) {

Int a, b, c; /* definition 1*/

. . .

While (. . .) {

Int b, c, d; /*definition 2*/

. . . <- - - - - - - - - - - - - - - 2

}

. . . <- - - - - - - - - - - - - - - 3

}

. . . <- - - - - - - - - - - - - - - 4

}

For each of the four marked points in this function, list each visible variable, along with the number of the definition statement that defines it.

Explanation / Answer

(8)

Sub1 gets its value of X from Sub1

Sub2 gets its value of X from Sub1

Sub3 gets its value of X from Main

(a)Assume the static scoping in the following points of execution of X is
i.    Sub1 gets the value of X from Sub1
ii.   Sub2 gets the value of X from Sub1
iii. Sub3 gets the value of X from Main

(b)

b) Let (a) for dynamic scoping

i.    Sub1 gets the value of X from Sub1
ii.   Sub2 gets the value of X from Sub1
iii. Sub3 gets the value of X from Sub1

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