HP HP-21 - Afterword

52 Function Keys
Afterword
If you have worked completely through this handbook, you
should have a very good knowledge of all of the basic functions
of the HP-21. But in fact you’ve only begun to see the power
of the calculator. You’ll come to understand it better and
appreciate it more as you use the HP-21 daily to solve even
the most complex mathematical expressions. At your fingertips
you have a tool that was unavailable to Archimedes, Galileo,
or Einstein. The only limits to the flexibility of the HP-21 are
the limits of your own mind.