Idiomatically determine all the lowercase and uppercase letters

Idiomatically determine all the lowercase and uppercase letters is a draft programming task. It is not yet considered ready to be promoted as a complete task, for reasons that should be found in its talk page.

Idiomatically determine all the lowercase and uppercase letters (of the alphabet) being used currently by a computer programming language.

Thr method should find the letters regardless of the hardware architecture that is being used   (ASCII, EBCDIC, or other).

task requirements

Display the set of all

• lowercase letters
• uppercase letters

that can be used (allowed) by the program.
You may want to mention what hardware architecture is being used, and if applicable, the operating system.

REXX

<lang rexx>/*REXX program determines what characters are lower- & uppercase letters*/ $L= /*set lowercase alphabet to null.*/ $U= /* " " " " " */

   do j=0  for 2**8                   /*traipse through all the chars. */
   _=d2c(j)                           /*convert decimal number to char.*/
   if datatype(_,'L')  then $L=$L||_  /*Lowercase?   Then add to list. */
   if datatype(_,'U')  then $U=$U||_  /*Uppercase?     "   "   "   "   */
   end   /*j*/                        /* [↑] put all letters into lists*/

say ' lowercase letters: ' $L /*display all lowercase letters. */ say ' uppercase letters: ' $U /* " " uppercase " */

                                      /*stick a fork in it, we're done.*/</lang>

The following REXX interpreters where used:

• PC/REXX
• Personal REXX
• R4
• ROO
• Regina (versions 3.2 ───► 3.7, all languages that are supported)

All were were executed on a (ASCII) PC using Windows/XP and Windows/7 with code page 437 in a DOS window.

    lowercase letters:  abcdefghijklmnopqrstuvwxyz
    uppercase letters:  ABCDEFGHIJKLMNOPQRSTUVWXYZ