Clarify universal-newline wording in tutorial (issue #16266).
diff --git a/Doc/tutorial/inputoutput.rst b/Doc/tutorial/inputoutput.rst
index 73143be..1324359 100644
--- a/Doc/tutorial/inputoutput.rst
+++ b/Doc/tutorial/inputoutput.rst
@@ -256,9 +256,10 @@
:dfn:`binary mode`: now the data is read and written in the form of bytes
objects. This mode should be used for all files that don't contain text.
-In text mode, the default is to convert platform-specific line endings (``\n``
-on Unix, ``\r\n`` on Windows) to just ``\n`` on reading and ``\n`` back to
-platform-specific line endings on writing. This behind-the-scenes modification
+In text mode, the default when reading is to convert platform-specific line
+endings (``\n`` on Unix, ``\r\n`` on Windows) to just ``\n``. When writing in
+text mode, the default is to convert occurrences of ``\n`` back to
+platform-specific line endings. This behind-the-scenes modification
to file data is fine for text files, but will corrupt binary data like that in
:file:`JPEG` or :file:`EXE` files. Be very careful to use binary mode when
reading and writing such files.