One standard predefined Prolog predicate is called "name".
It is a two argument rule that converts an atom (e.g. matthew), 
being the first argument, into a list of ASCII codes 
(matthew being [109,97,116,116,104,101,119]),  and vice-versa.

e.g. name(bill,Name).
Name=[98,105,108,108].
Yes.

name(Isem,[108,101,108,105]).
Isem=leli.
Yes.

name(Char,[97]).
Char=a.
Yes.

Problem:  Write a rule 'caps' with two arguments (denoted as caps/2) which 
converts a character entered by the user as a first argument, to uppercase 
(the second argument), if its' lowercase - otherwise leaves it alone.
unchanged.

e.g.  caps(a,X).
X='A'.
Yes

caps(3,X).
X=3.
Yes.