hp 71b
this unit was very generously given to me by tony duell and has enabled
me to evaluate the hands on experience. for example, the 71b has a built-in calculator mode. although primarily
a pocket computer, hp did not forsake the ability to pick up and calculate
manually. this mode works well, with recall, editing and correction.
interestingly for hp, the calculation mode is not rpn the unit is highly expandable, with four expansion ports. it has 16k ram
as standard, which is adequate for useful programs right away. the unit programs
in an extended variant of of special interest to me is the fact that this model has a number system
based on unfortunately ieee-854 does not yield the same 15 digit accuracy as 754, the mantissa is 12 digits and the exponent +/-499. making this the first calculator to have exponents larger than 99 but otherwise of comparable precision to most 10 digit models (who typically have 2 internal guard digits). the implementation of the operating system is superb. there is even a real
time clock and calendar. its even possible to switch itself off and wake up
later and continue under software control. there is a hardware my only reservations are that the screen could have benefited from being wider or even to have had two lines. also, why is the backspace key shifted. this felt a little odd. the machine is greatly enhanced with the addition of the math rom. this rom
adds native support for complex numbers to all scientific functions. in fact,
the complex number support is even better than the 15c
as matrices can also be complex and of larger sizes (memory permitting). root
finding an numerical integration can be performed using formulae directly from
the command line (eg (1) although you can never remember how to chain on calculations after not using the machine for some time which is really annoying. |