<li><h3><a href="UBT-PREHISTORY.html">UBT-PREHISTORY</a> -- undo the <a href="COMMAND.html">command</a>s back through the last <code><a href="RESET-PREHISTORY.html">reset-prehistory</a></code> event
82
</h3>
83
</li>
84
85
<li><h3><a href="UBU.html">UBU</a> -- undo the <a href="COMMAND.html">command</a>s back up to (not including) a <a href="COMMAND.html">command</a> descriptor
86
</h3>
87
</li>
88
89
<li><h3><a href="UBU_bang_.html">UBU!</a> -- undo <a href="COMMAND.html">command</a>s, without a query or an error
90
</h3>
91
</li>
92
81
93
</ul>
82
94
83
95
ACL2 keeps track of the <a href="COMMAND.html">command</a>s that you have executed that have