The Museum of HP Calculators   In the late 1980s, HP was
developing a new series of extremely powerful calculators that
needed a new programming language. For earlier calculators,
memory was very expensive and bulky and the challenge for
firmware writers was to pack a set of scientific functions into
very little space. They used machine language exclusively and
carefully refined and re-refined their algorithms until they
fit. However, as memory became denser and less expensive, the
major challenge shifted away from saving space to implementing
and testing the many sophisticated functions that newer
calculators contained.  HP examined existing languages such as
BASIC but found them to be unsuitable both because of their
limitations and their resource demands which were still rather
high for pocket devices. Instead, HP combined elements of RPN,
Lisp and Forth and came up with a language called Reverse Polish
Lisp or RPL. From Lisp, RPL inherited concepts such as atomic
and composite objects, temporary (lambda)