Problem Statement

Idiomatically determine all the lowercase and uppercase letters   (of the Latin [English] alphabet)   being used currently by a computer programming language. The method should find the letters regardless of the hardware architecture that is being used (ASCII, EBCDIC, or other).

Display the set of all: that can be used (allowed) by the computer program, where   letter   is a member of the Latin (English) alphabet:     a ──► z     and     A ──► Z.

You may want to mention what hardware architecture is being used, and if applicable, the operating system.

Let's start with the solution:

#lang racket
(require srfi/14)
(printf "System information: ~a~%" (map system-type (list 'os 'word 'machine)))
(printf "All lowercase characters: ~a~%" (char-set->string char-set:lower-case))
(newline)
(printf "All uppercase characters: ~a~%" (char-set->string char-set:upper-case))