The HP-15C is a high-end scientific pocket calculator with a root-solver and numerical integration. A member of Hewlett-Packard Voyager series of programmable calculators, it was produced between 1982 and 1989. The processor used the then new technology of Silicon on Sapphire that allowed ultra-low consumption. The 3 button batteries provided often lasted decades!
For many users, it is the pinnacle of HP calculator engineering together with the HP42s. Due to its popularity, and based on the then-new HP12c ARM-based platform, it was reintroduced in 2011 as HP15c Limited Edition. It was 150 times faster than the original, but it had higher consumption and the batteries would last around 4 months or normal use.
The main capabilities were outstanding, considering the limited keyboard:
• All kind of trigonometric functions, including inverses, hyperbolics and hyperbolic inverses, in degrees, radians and gradiants
• Logarithms (log(x) and ln(x)) and exponentials (10x and ex)
• % and % increase
• Conversions and number manipulations
◦ Rectangular to polar and vice-versa
◦ H.MS to decimal hours and vice-versa
◦ Degrees to radians and vice-versa
◦ Integer part and fractional part
• Complex numbers, working seamlessly on most available functions
◦ Full 4-level complex stack (instead of the two level of HP41 Advantage pac or Math pac)
◦ Real to imaginary exchange in a single step
◦ Rectangular to Polar and Polar to rectangular also work seamlessly with complex operands.
• Matrices, with full featured operations up to 8x8 size:
◦ Copy and paste matrices
◦ Multiplication, addition, subtraction – scalar and matrix
◦ Transposing a matrix – taking also care of the dimension change if needed
◦ Matrix inversion
◦ System solving – a short cut: instead of A-1B you call to stack B, then A and divide!
◦ LU decomposition
◦ Determinant
◦ Row norm
◦ Frobenius norm
◦ Working with complex matrices in two different ways
• Basic statistics
◦ Permutations and combinations
◦ 2-variable statistics: sum of x, sum of y, sum of x2, sum of y2, sum of xy
◦ Average and standard deviation
◦ Linear regression
◦ Factorial, but not just the integer factorial (n!) but the extended non-integer version (gamma function)
• Integral for arbitrary functions (defined as programs)
• Solve: find the zeros of arbitrary functions, defined as programs
• Storage: up to 65 registers + I (index) register
◦ Register arithmetic to shorten programs and keystrokes: RCL+, STO+ and with the rest of arithmetic operators.
• Programming: up to 448 programming steps
◦ up to 25 labels: A to E, 0 to 9, .0 to .9
◦ GTO and GSB; use of index register
Some HP15c related links