bpo-35099: Update idlelib/help.html (GH-10353)

(This should have been done with the first PR for this issue.)
(cherry picked from commit f1d3efc)

Co-authored-by: Terry Jan Reedy <tjreedy@udel.edu>

Lib/idlelib/help.html

@@ -616,23 +616,33 @@ <h3>Startup failure<a class="headerlink" href="#startup-failure" title="Permalin
 <p>If IDLE quits with no message, and it was not started from a console, try
 starting from a console (<code class="docutils literal notranslate"><span class="pre">python</span> <span class="pre">-m</span> <span class="pre">idlelib)</span></code> and see if a message appears.</p>
 </div>
-<div class="section" id="idle-console-differences">
-<h3>IDLE-console differences<a class="headerlink" href="#idle-console-differences" title="Permalink to this headline">¶</a></h3>
+<div class="section" id="running-user-code">
+<h3>Running user code<a class="headerlink" href="#running-user-code" title="Permalink to this headline">¶</a></h3>
 <p>With rare exceptions, the result of executing Python code with IDLE is
-intended to be the same as executing the same code in a console window.
+intended to be the same as executing the same code by the default method,
+directly with Python in a text-mode system console or terminal window.
 However, the different interface and operation occasionally affect
-visible results.  For instance, <code class="docutils literal notranslate"><span class="pre">sys.modules</span></code> starts with more entries.</p>
-<p>IDLE also replaces <code class="docutils literal notranslate"><span class="pre">sys.stdin</span></code>, <code class="docutils literal notranslate"><span class="pre">sys.stdout</span></code>, and <code class="docutils literal notranslate"><span class="pre">sys.stderr</span></code> with
-objects that get input from and send output to the Shell window.
-When Shell has the focus, it controls the keyboard and screen.  This is
+visible results.  For instance, <code class="docutils literal notranslate"><span class="pre">sys.modules</span></code> starts with more entries,
+and <code class="docutils literal notranslate"><span class="pre">threading.activeCount()</span></code> returns 2 instead of 1.</p>
+<p>By default, IDLE runs user code in a separate OS process rather than in
+the user interface process that runs the shell and editor.  In the execution
+process, it replaces <code class="docutils literal notranslate"><span class="pre">sys.stdin</span></code>, <code class="docutils literal notranslate"><span class="pre">sys.stdout</span></code>, and <code class="docutils literal notranslate"><span class="pre">sys.stderr</span></code>
+with objects that get input from and send output to the Shell window.
+The original values stored in <code class="docutils literal notranslate"><span class="pre">sys.__stdin__</span></code>, <code class="docutils literal notranslate"><span class="pre">sys.__stdout__</span></code>, and
+<code class="docutils literal notranslate"><span class="pre">sys.__stderr__</span></code> are not touched, but may be <code class="docutils literal notranslate"><span class="pre">None</span></code>.</p>
+<p>When Shell has the focus, it controls the keyboard and screen.  This is
 normally transparent, but functions that directly access the keyboard
-and screen will not work.  If <code class="docutils literal notranslate"><span class="pre">sys</span></code> is reset with <code class="docutils literal notranslate"><span class="pre">importlib.reload(sys)</span></code>,
-IDLE’s changes are lost and things like <code class="docutils literal notranslate"><span class="pre">input</span></code>, <code class="docutils literal notranslate"><span class="pre">raw_input</span></code>, and
-<code class="docutils literal notranslate"><span class="pre">print</span></code> will not work correctly.</p>
-<p>With IDLE’s Shell, one enters, edits, and recalls complete statements.
-Some consoles only work with a single physical line at a time.  IDLE uses
-<code class="docutils literal notranslate"><span class="pre">exec</span></code> to run each statement.  As a result, <code class="docutils literal notranslate"><span class="pre">'__builtins__'</span></code> is always
-defined for each statement.</p>
+and screen will not work.  These include system-specific functions that
+determine whether a key has been pressed and if so, which.</p>
+<p>IDLE’s standard stream replacements are not inherited by subprocesses
+created in the execution process, whether directly by user code or by modules
+such as multiprocessing.  If such subprocess use <code class="docutils literal notranslate"><span class="pre">input</span></code> from sys.stdin
+or <code class="docutils literal notranslate"><span class="pre">print</span></code> or <code class="docutils literal notranslate"><span class="pre">write</span></code> to sys.stdout or sys.stderr,
+IDLE should be started in a command line window.  The secondary subprocess
+will then be attached to that window for input and output.</p>
+<p>If <code class="docutils literal notranslate"><span class="pre">sys</span></code> is reset by user code, such as with <code class="docutils literal notranslate"><span class="pre">importlib.reload(sys)</span></code>,
+IDLE’s changes are lost and input from the keyboard and output to the screen
+will not work correctly.</p>
 </div>
 <div class="section" id="developing-tkinter-applications">
 <h3>Developing tkinter applications<a class="headerlink" href="#developing-tkinter-applications" title="Permalink to this headline">¶</a></h3>
@@ -752,7 +762,7 @@ <h3><a href="../contents.html">Table of Contents</a></h3>
 <li><a class="reference internal" href="#startup-and-code-execution">Startup and code execution</a><ul>
 <li><a class="reference internal" href="#command-line-usage">Command line usage</a></li>
 <li><a class="reference internal" href="#startup-failure">Startup failure</a></li>
-<li><a class="reference internal" href="#idle-console-differences">IDLE-console differences</a></li>
+<li><a class="reference internal" href="#running-user-code">Running user code</a></li>
 <li><a class="reference internal" href="#developing-tkinter-applications">Developing tkinter applications</a></li>
 <li><a class="reference internal" href="#running-without-a-subprocess">Running without a subprocess</a></li>
 </ul>
@@ -841,7 +851,7 @@ <h3>Navigation</h3>
 <br />
     <br />
 
-    Last updated on Oct 28, 2018.
+    Last updated on Nov 05, 2018.
     <a href="https://docs.python.org/3/bugs.html">Found a bug</a>?
     <br />