The Museum of HP Calculators The Museum of HP Calculators
Features in optional ROMs are listed as Option. Features in HP mag card or tape Application Pacs are listed as +. Other software is not included. |
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|---|---|
| Display and Keyboard | HP-91 |
| Display type | LED |
| Display format | 1 Line |
| FIXed number format | Yes |
| SCIentific number format | Yes |
| ENGineering number format | Yes |
| STanDard / ALL number format | - |
| Alpha messages and prompts | - |
| Softkeys labeled by mag. card or overlay | - |
| Softkeys labeled by display menus | - |
| Softkeys with neither labeling system | - |
| Status annunciators | - |
| Redefinable keyboard | - |
| Logic | HP-91 |
| Logic system | RPN |
| Stack levels | 4 |
| Last x | Yes |
| Undo | - |
| Precedence | - |
| Parentheses | - |
| Storage Addition (STO +) | Yes |
| Storage Arithmetic (STO +, −, ×, ÷) | Yes |
| Storage Exponentiation (STO ^) | - |
| Recall Arithmetic | - |
| Named variables | - |
| Multiple data types | - |
| Directories | - |
| Math | HP-91 |
| +, −, ×, ÷ | Yes |
| 1/x | Yes |
| √ | Yes |
| x2 | Yes |
| LOG x | Yes |
| 10x | Yes |
| LN x | Yes |
| ex | Yes |
| yx | Yes |
| π | Yes |
| % | Yes |
| % change | Yes |
| INTeger truncation and ABSolute value | - |
| Trigonometric functions (SIN, COS etc.) | Yes |
| Hyperbolic trig. (SINH, COSH etc.) | - |
| # of trig. modes (degrees, radians, grads) | 3 |
| Advanced Math | HP-91 |
| Solver / root finder | - |
| Numeric integration | - |
| Complex numbers | - |
| Matrix operations | - |
| Matrix writer | - |
| Equation writer | - |
| Symbolic operations | - |
| Fractions | - |
| Plotting and graphics (display) | - |
| Plotting and graphics (printer / plotter) | - |
| Statistical | HP-91 |
| Mean, standard deviation (# of variables) | 2 |
| Σ of n, x, x2 | Yes |
| Σ of n, x, x2, y | Yes |
| Σ of n, x, x2, y, xy | Yes |
| Σ of n, x, x2, y, y2, xy | Yes |
| Σ of lists | - |
| Random number generator | - |
| Linear regression, estimate | Yes |
| Curve fitting | - |
| Correlation coefficient | - |
| Normal distribution | - |
| Factorial | Yes |
| Gamma | - |
| Combinations and permutations | - |
| Scientific and Time | HP-91 |
| Polar / rectangular conversions | Yes |
| Base conversions (2, 8, 10, 16) | - |
| Arithmetic in bases 2, 8 and 16 | - |
| Bit operations (AND, OR, XOR, ...) | - |
| Selectable word size (1-64 bits) | - |
| Selectable complement mode (1's, 2's, unsigned) | - |
| Decimal hrs / hrs.min.sec. conversions | Yes |
| Hrs.min.sec arithmetic | Yes |
| Time of day clock | - |
| Timer | - |
| Dynamic calculations (timer × rate) | - |
| Alarms | - |
| Unit Conversions | HP-91 |
| Centimeters / inches | - |
| Millimeters / inches | - |
| Meters / feet | - |
| Kilograms / pounds (mass) | - |
| Newtons / pounds (force) | - |
| British thermal units / joules | - |
| Liters / gallons | - |
| ° Celsius / ° Fahrenheit | - |
| Other | - |
| User-defined units | - |
| Time Value of Money | HP-91 |
| Number of payments (n) | - |
| Interest rate (i) | - |
| Present Value (PV) | - |
| Payment (PMT) | - |
| Future Value (FV) | - |
| Cash Flow Analysis | HP-91 |
| Net present value (NPV) | - |
| Internal rate of return (IRR) | - |
| Amortization | HP-91 |
| Accumulated Interest (ACC INT) | - |
| Balance (BAL) | - |
| Depreciation | HP-91 |
| Straight line (SL) | - |
| Sum of the years digits (SOYD) | - |
| Declining balance (DB) | - |
| Bonds and calendar functions | HP-91 |
| Bond price | - |
| Bond yield | - |
| Date arithmetic / calendar functions | - |
| Memory and Programming | HP-91 |
| Programming language(s) | - |
| RAM / Max # of variables or addressable registers | 16 registers |
| Max # of program steps | - |
| RAM / Max vars or regs with full optional RAM | - |
| Max # of prog steps with full optional RAM | - |
| Merged program steps | - |
| Manual register / program memory allocation | - |
| Automatic register / program memory allocation | - |
| Overlapped register and program memory | - |
| Continuous memory | - |
| Flags | - |
| Conditional tests | - |
| Subroutine levels | - |
| Indexed looping (increment by +/- 1, end at 0) | - |
| Indexed looping (choice of increment and end) | - |
| Multiple index / loop registers | - |
| Line number addressing | - |
| Branching by relative line number | - |
| Global program label addressing | - |
| Local program label addressing | - |
| Indirect / computed addressing and control | - |
| Multiple indirection registers | - |
| Pause | - |
| Alpha messages and prompts in programs | - |
| Alpha program listings | - |
| Alpha string manipulation | - |
| Program step insert / delete | - |
| I/O and Expansion Features | HP-91 |
| ROM modules | - |
| RAM modules or expansion option | - |
| General expansion slots / connector | - |
| Magnetic card reader/writer | - |
| Tape drive | - |
| Disk drive | - |
| Upgradeable firmware | - |
| Optical wand | - |
| Serial port | - |
| Infrared input | - |
| Infrared output | - |
| Printer | Yes |
| Networking | - |
| Other | - |
| General | HP-91 |
| Sounds | - |
| Self test | - |
| Hard case (in addition to soft case) | - |
| Additional Features | - |
| Batteries | Rechargeable |
| Length (inches) | 9" |
| Width | 8" |
| Height | 2.5" |
| Weight (oz or lbs) | 2.5 lbs |
| Year of introduction | 1976 |
Features in optional ROMs are listed as Option. Features in HP mag card or tape Application Pacs are listed as +. Other software is not included. Unlim means limited only by available memory. |
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