HP-20S

Libraries

• A- finder, finds a root of f=0
• B- integral, calculates definite integral using Simpson method
• C- complex numbers manipulations
• D- matrix manipulations and line equations solver
• E- quadratic equation solver
• F- curve fitting, using exponential, logarithmic and power functions

  Design peculiarities

• INPUT and SWAP keys, which are awkward and not clear solution to mimic RPN functionality.
• Absence of "x
• A real bug is "x<=y" test. First of all, its name is misleading. Really, it is "x>=y" test in terms of RPN calculators. The manual says that x is 'hidden' while y is 'visible'. But y^x power key on the calculator's keyboards functions in the traditional fashion of other HP RPN calculators. The second problem here is due to algebraic design: in order to separate two arguments of a test should the user divide them either with arithmetic operation or INPUT. If using arithmetic, like: