Privileg PR-56D-NC
Datasheet legend
Ab/c:
Fractions calculation
AC: Alternating current BaseN: Number base calculations Card: Magnetic card storage Cmem: Continuous memory Cond: Conditional execution Const: Scientific constants Cplx: Complex number arithmetic DC: Direct current Eqlib: Equation library Exp: Exponential/logarithmic functions Fin: Financial functions Grph: Graphing capability Hyp: Hyperbolic functions Ind: Indirect addressing Intg: Numerical integration Jump: Unconditional jump (GOTO) Lbl: Program labels LCD: Liquid Crystal Display LED: Light-Emitting Diode Li-ion: Lithium-ion rechargeable battery Lreg: Linear regression (2-variable statistics) mA: Milliamperes of current Mtrx: Matrix support NiCd: Nickel-Cadmium rechargeable battery NiMH: Nickel-metal-hydrite rechargeable battery Prnt: Printer RTC: Real-time clock Sdev: Standard deviation (1-variable statistics) Solv: Equation solver Subr: Subroutine call capability Symb: Symbolic computing Tape: Magnetic tape storage Trig: Trigonometric functions Units: Unit conversions VAC: Volts AC VDC: Volts DC |
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Privileg PR-56D-NC
As popular a "store brand" in Germany as Radio Shack is in the United States, Privileg released many OEM calculators during the seventies. Some of these, the PR56D-NC among them, were programmable. Its programming model is a telltale version common to calculators that use MOS chipsets, and similar to the classic Commodore PR-100. (Another calculator with the same chipset that's used in the PR56D-NC is the Sanyo CZ-0911PG.)
Despite their obvious limitations, I remain curiously attached to calculators of this type. No doubt it is due to the fact that the first programmable I ever owned, a Hungarian version of the PR-100, had the same programming model. Although the PR-100 has more functions, the PR56D-NC has a huge advantage when it comes to programming: its programming model is partially merged, meanings that the ARC/F (second function) key does not count as an extra keystroke. This subtle difference can mean a huge savings in program steps, making it possible to implement algorithms that just wouldn't fit into the 72-step unmerged program space of the PR-100.
Case in question: my favorite programming example, the Gamma function. Just today I received an e-mail from Robert H. Windschitl who showed that Stirling's formula can, in fact, be used to derive another approximation, particularly efficient because it requires no constants that consume either precious register space or an inordinate number of programming steps. His approximation requires the hyperbolic sine function; although not present on the PR56D-NC's keyboard, it can be computed easily enough (sinh x=(e^{x}-e^{-x})/2). Even with a correction factor and an iterative loop for arguments less than 3, the program conveniently fits into the calculator's 72-step program memory:
00 55 STO 01 101 1 02 55 STO 03 100 0 04 11 - 05 105 3 06 10 + 07 96 SKIP 08 93 GOTO 09 101 1 10 108 8 11 106 4 12 80 = 13 52 M× 14 101 1 15 93 GOTO 16 100 0 17 102 2 18 105 3 19 80 = 20 17 1/x 21 42 ex 22 11 - 23 64 x-y 24 17 1/x 25 13 ÷ 26 102 2 27 12 × 28 56 RCL 29 100 0 30 10 + 31 81 ( 32 56 RCL 33 100 0 34 18 x2 35 18 x2 36 17 1/x 37 13 ÷ 38 56 RCL 39 100 0 40 18 x2 41 13 ÷ 42 108 8 43 101 1 44 100 0 45 80 = 46 19 √ 47 12 × 48 56 RCL 49 100 0 50 13 ÷ 51 101 1 52 42 ex 53 14 yx 54 56 RCL 55 100 0 56 12 × 57 81 ( 58 102 2 59 12 × 60 65 π 61 12 × 62 56 RCL 63 100 0 64 82 ) 65 19 √ 66 13 ÷ 67 56 RCL 68 101 1 69 80 =