Introduction ix
Matrix functionality was built in to handle up to an 8 × 8 matrix. Functions
provided included finding determinants, inverses, LU decomposition,
scalar and matrix arithmetic, transpose, solving systems of equations,
norms, residuals, and transformations. These abilities were not lost on
students and professionals alike. The HP-15C remained highly popular!
Nevertheless, as technology moved on, HP replaced the HP-15C with a
range of later models. These had more features and greater speed than
the HP-15C, yet users yearned for the HP-15C’s particular characteristics,
including the horizontal layout. Prices for secondhand units rose steadily,
and former users pressed HP to bring the HP-15C back. After all, if HP
continued to make the HP-12C, could they not use the same basic model
to build a revived HP-15C? In 2011 HP did produce a limited number of HP-
15C units, described as the HP 15c Limited Edition.
The HP 15c Collector’s Edition
Now, a further 12 years later, you have in your hands a second revival: the
HP 15c Collector’s Edition. Yet it is not just for collectors—it is a powerful
calculator in its own right, faster and with more memory than the original
HP-15C. The HP 15c CE now provides:
672 bytes of program memory (one or two bytes per instruction),
increased from 448, while retaining the HP-15C’s sophisticated
programming capability, including conditional and unconditional
branching, subroutines, flags, and editing.
Direct and indirect storage in up to 99 registers, increased from 67.
In general the extra memory and speed are an advantage, but there will
be some cases where care is needed:
If a program written for the original HP-15C relies on special timing,
for example if a program gives the user a fixed time to react, then
that program will need to be slowed down on the HP 15c CE,
possibly by the addition of © (pause) steps or by making loops
repeat more times. This is described in more detail in Appendix G.
The original self-tests for the HP-15C will not work with the new
platform of the HP 15c CE and have been replaced with new tests
described in Appendix F.
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