. We have seen the explanation of this parse above.  What we want to do in <code class="docutils literal notranslate"><span class="pre">move_3_4</span></code> is to change the overall “case” instruction in the beginning from <code class="docutils literal notranslate"><span class="pre">11#####</span></code> to <code class="docutils literal notranslate"><span class="pre">111#####</span></code>.   And each time our program writes to a register, we want that register to be R4, not R1.  So we make two change