GATE | GATE-CS-2001 | Question 44

Consider the following program

Program P2
    var n: int:
     procedure W(var x: int)
     begin
         x=x+1;
         print x;
     end

     procedure D
     begin
         var n: int;
         n=3;
         W(n);
     end
begin //beginP2
  n=10;
  D;
end

If the language has dynamic scoping and parameters are passed by reference, what will be printed by the program?
(A) 10
(B) 11
(C) 3
(D) None of the above


Answer: (D)

Explanation:

In static scoping or compile-time scoping the free variables (variables used in a function that are neither local variables nor parameters of that function) are referred as global variables because at compile only global variables are available.
In dynamic scoping or run-time scoping the free variables are referred as the variables in the most recent frame of function call stack. In the given code in the function call of procedure W the local variable x is printed i.e 4. Under dynamic scoping if x would have not been there in procedure W then we would refer to x of the function in function call stack i.e procedure D and the main function but since x is a local variable not a free variable we referred to the local variable hence 4 will be printed.

See question 4 of https://www.geeksforgeeks.org/principle-of-programming-languages-set-1/

This solution is contributed by Parul Sharma.

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