What are called Parameters and write a note on
(i) Parameter without Type
(ii) Parameter with Type

Identify in the following program

let rec gcd a b:=            if b <> 0 then gcd b (a mod b) else return a:

i) Name of the function
ii) Identify the statement which tells it is a recursive function
iii) Name of the argument variable
iv) Statement which invoke the function recursively
v) Statement which terminates the recursion

Explain with example Pure and impure functions.

Explain with an example interface and implementation.