The Museum of HP Calculators


HP-81 Features

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.

Display and Keyboard HP-81
Display type LED
Display format 1 Line
FIXed number format Yes*
SCIentific number format Modified*
ENGineering number format -
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-81
Logic system RPN
Stack levels 4
Last x -
Undo -
Precedence -
Parentheses -
Storage Addition (STO +) -
Storage Arithmetic (STO +, -, ×, ÷) -
Storage Exponentiation (STO ^) -
Recall Arithmetic -
Named variables -
Multiple data types -
Directories -
   
Math HP-81
+, -, ×, ÷ Yes 
1/x -
sq. root Yes
x2 -
LOG x Yes
10x -
LN x -
ex -
yx Yes
pi -
% Yes
% change Yes
INTeger truncation and ABSolute value -
Trigonometric functions (SIN, COS etc.) -
Hyperbolic trig. (SINH, COSH etc.) -
# of trig. modes (degrees, radians, grads) -
   
Advanced Math HP-81
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-81
Mean, standard deviation (# of variables) 1
Summation of n, x, x2 Yes
Summation of n, x, x2, y -
Summation of n, x, x2, y, xy -
Summation of n, x, x2, y, y2, xy -
Summation of lists -
Random number generator -
Linear regression, estimate  Yes
Curve fitting Yes
Correlation coefficient -
Normal distribution -
Factorial -
Gamma -
Combinations and permutations -
   
Scientific and Time

HP-81

Polar / rectangular conversions -
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 -
Hrs.min.sec arithmetic -
Time of day clock -
Timer -
Dynamic calculations (timer × rate) -
Alarms -
   
Unit Conversions

HP-81

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-81
Number of payments (n) Yes
Interest rate (i) Yes
Present Value (PV) Yes
Payment (PMT) Yes
Future Value (FV) Yes
   
Cash Flow Analysis HP-81
Net present value (NPV) -
Internal rate of return (IRR) Yes
   
Amortization HP-81
Accumulated Interest (ACC INT) Yes
Balance (BAL) Yes
   
Depreciation HP-81
Straight line (SL) Yes
Sum of the years digits (SOYD) Yes
Declining balance (DB) Yes
   
Bonds and calendar functions HP-81
Bond price Yes
Bond yield Yes
Date arithmetic / calendar functions Yes
   
Memory and Programming HP-81
Programming language(s) -
RAM / Max # of variables or addressable registers 20 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-81
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 -
Networking -
Other -
   
General HP-81
Sounds -
Self test -
Hard case (in addition to soft case) Yes
Additional Features -
Batteries -
Length (inches) 15.4"
Width 10.9"
Height 5.6"
Weight (oz or lbs) 13.2 lbs
Year of introduction 1973

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.

HP-81 notes:
  • This was a printing version of the HP-80 that also added a number of new features.
  • The shift key followed by 0-6 set FIXed mode with that many digits. The shift key followed by 7-9 set SCIentific mode.
  • SAVE key instead of ENTER key.

Go to the feature comparison page
Go back to the main exhibit hall