Hewlett-Packard HP-55
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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Hewlett-Packard HP-55
The HP-55 is a unique calculator. A cheaper alternative to the HP-65, it had no magnetic cards; what it had instead was a built-in quartz timer, making it probably the first pocket-size calculator ever with such a capability. In timer mode, the R/S key was used to start or stop the timer, and while the timer was running, the number keys could be used to store the current value in a numbered register.
The story of my HP-55, received in non-working condition, began with a crushed transistor. Two display driver chips replaced, with inhuman effort, by identical chips taken from a thoroughly dead HP-65. Still, no working calculator. Then came the oscilloscope, the voltmeter, some headscratching, more measurements, circuit tracing, even more headscratching, mumbling, swearing, then a spark of inspiration: where, exactly, is this chip getting power from? And why isn't it getting it? I wonder... could this diode be faulty? Five minutes later: a working calculator in my hands. Now I can start exploring this beast that I just brought back to life...
The HP-55 had a fair number (20) of registers but a very small program memory. Only 49 program steps, and these were completely unmerged, with the exception of the GTO instruction that required only one step for the instruction itself and the line number. (Could this be the only HP calculator in which even register references are unmerged?) I would like to create a Gamma function program on this calculator for demonstration purposes, but in 49 program steps, it just doesn't seem possible.
Or does it? After all, I have not one, but two alternative solutions! I can sacrifice accuracy and satisfy myself with a program for Stirling's formula. Or, I can sacrifice speed and write a program that calculates the incomplete Gamma function (and, by extension, approximates the Gamma function itself) iteratively. Hmmm... why don't I do both?
Here's what Stirling's formula looks like on the HP-55:
01. 41 ENTER 02. 41 ENTER 03. 22 x-y 04. 02 2 05. 71 × 06. 31 f 07. 83 π 08. 71 × 09. 31 f 10. 42 √ 11. 22 x-y 12. 41 ENTER 13. 12 yx 14. 71 × 15. 22 x-y 16. 32 g 17. 22 ex 18. 81 ÷ 19. 22 x-y 20. 13 1/x 21. 01 1 22. 02 2 23. 81 ÷ 24. 01 1 25. 61 + 26. 71 ×
Fast, simple, and inaccurate. To use the program, enter the argument and press BST (to reset the program counter) followed by R/S.
The incomplete Gamma function program is listed below. To use, enter the function argument, hit ENTER, then enter the integration limit, hit BST, and hit R/S. Execution time may be several minutes, depending on the integration limit used. Note that this version works only for positive arguments.
01. 33 STO 02. 01 1 03. 22 x-y 04. 33 STO 05. 02 2 06. 12 yx 07. 34 RCL 08. 02 2 09. 81 ÷ 10. 33 STO 11. 03 3 12. 34 RCL 13. 01 1 14. 34 RCL 15. 02 2 16. 01 1 17. 61 + 18. 33 STO 19. 02 2 20. 81 ÷ 21. 34 RCL 22. 03 3 23. 71 × 24. 33 STO 25. 03 3 26. 61 + 27. 32 g 28. -30 x=y 30 29. -12 GTO 12 30. 34 RCL 31. 01 1 32. 32 g 33. 22 ex 34. 81 ÷