Add explanation for machine-specific configuration of Python and R

module2/ressources/rr_org/init.el

+;; Machine-dependent configuration - adapt as required for your computer!
+
+;; If a full path to the interpreter is used, be careful it if contains spaces
+;; (which seems to be typical for Windows and not rare for macOS). The path
+;; must then be surrounded by backslash-escaped quotation marks, as in
+;; (setq org-babel-python-command "\"C:/Program Files/Python/Python37/python.exe\"")
+(setq org-babel-python-command "python3")
+
+;; For Unix-like systems, this can be normally left commented out. Under Windows,
+;; insert the path to your R interpreter.
+;; (setq inferior-R-program-name "C:/Program Files/R/R-3.5.1/bin/x64/Rterm.exe")
+
 (require 'org)
 
 (setq inhibit-splash-screen t)
@@ -154,8 +166,6 @@ Entered on %U
      ))
   (setq org-src-preserve-indentation t)
 
-(setq org-babel-python-command "python3")
-
 (add-to-list 'org-structure-template-alist
         '("s" "#+begin_src ?\n\n#+end_src" "<src lang=\"?\">\n\n</src>"))
 

module2/ressources/rr_org/init.org

@@ -18,6 +18,29 @@ to work, you'll need:
 Backup you own =.emacs= if you have one and replace it with [[file:init.el][the content
 of this file]]. If you ever want to regenerate if from this org
 document, simply =M-x org-babel-tangle=.
+
+* Machine-dependent configuration
+For Linux, macOS, and other Unix-like systems, the following settings will probably work fine. If you use Windows, or if running Python and/or R code from OrgMode fails with an error message, please replace "python3" by the full path to your Python interpreter.
+
+#+begin_src emacs-lisp :tangle init.el
+;; Machine-dependent configuration - adapt as required for your computer!
+#+end_src
+
+** Python
+*** We use python3
+#+begin_src emacs-lisp :tangle init.el
+;; If a full path to the interpreter is used, be careful it if contains spaces
+;; (which seems to be typical for Windows and not rare for macOS). The path
+;; must then be surrounded by backslash-escaped quotation marks, as in
+;; (setq org-babel-python-command "\"C:/Program Files/Python/Python37/python.exe\"")
+(setq org-babel-python-command "python3")
+#+end_src
+** R
+#+begin_src emacs-lisp :tangle init.el
+;; For Unix-like systems, this can be normally left commented out. Under Windows,
+;; insert the path to your R interpreter.
+;; (setq inferior-R-program-name "C:/Program Files/R/R-3.5.1/bin/x64/Rterm.exe")
+#+end_src
 * Loading files:  
 ** Loading babel: 						     :ARNAUD:
 #+begin_src emacs-lisp :tangle init.el
@@ -280,11 +303,6 @@ Additional shortcuts for navigating through org-mode documents:
   (setq org-src-preserve-indentation t)
 #+end_src
 
-** Python
-*** We use python3
-#+begin_src emacs-lisp :tangle init.el
-(setq org-babel-python-command "python3")
-#+end_src
 ** Adding source code blocks: 					       :LUKA:
 *** With capital letters:
 To use this type <s and then TAB