ISRO | ISRO CS 2018 | Question 79

Let P be a procedure that for some inputs calls itself (i.e. is recursive). If P is guaranteed to terminate, which of the following statement(s) must be true?

I.   P has a local variable
II.  P has an execution path where it does not call itself
III. P either refers to a global variable or has at least one parameter

(A) I only
(B) II only
(C) III only
(D) II and III only


Answer: (D)

Explanation: In any recursive procedure:
a) A base condition is always required, so that, the procedure can terminate its repeated execution while returning some value to the main() function. So, statement (II) is necessary.
b) a recursive function should either refers to a global variable or has at least one parameter so that it can be recursively called creating a new copy of local variables in the stack. In the absence of these, there would be no purpose of a recursive procedure as it will not be able to execute.

So, option (D) is correct.

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