The Museum of HP Calculators

HP 9815A 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 9815A
Display type Gas Plasma
Display format 1 Line
FIXed number format Yes
SCIentific number format Yes
ENGineering number format Yes*
STanDard / ALL number format -
Alpha messages and prompts On printer
Softkeys labeled by mag. card or overlay Yes
Softkeys labeled by display menus -
Softkeys with neither labeling system -
Status annunciators -
Redefinable keyboard -
Logic HP 9815A
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 9815A
+, −, ×, ÷ Yes 
1/x Yes
x2 Yes
LOG x Yes
10x Yes
LN x Yes
ex Yes
yx Option
π Yes
% -
% change -
INTeger truncation and ABSolute value Yes
Trigonometric functions (SIN, COS etc.) Yes
Hyperbolic trig. (SINH, COSH etc.) -
# of trig. modes (degrees, radians, grads) 3
Advanced Math HP 9815A
Solver / root finder -
Numeric integration -
Complex numbers Limited
Matrix operations -
Matrix writer -
Equation writer -
Symbolic operations -
Fractions -
Plotting and graphics (display) -
Plotting and graphics (printer / plotter) Option
Statistical HP 9815A
Mean, standard deviation (# of variables) 1
Σ of n, x, x2 Yes
Σ of n, x, x2, y -
Σ of n, x, x2, y, xy -
Σ of n, x, x2, y, y2, xy -
Σ of lists -
Random number generator -
Linear regression, estimate  -
Curve fitting -
Correlation coefficient -
Normal distribution -
Factorial -
Gamma -
Combinations and permutations -
Scientific and Time HP 9815A
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 -
Time of day clock -
Timer -
Dynamic calculations (timer × rate) -
Alarms -
Unit Conversions HP 9815A
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 9815A
Number of payments (n) -
Interest rate (i) -
Present Value (PV) -
Payment (PMT) -
Future Value (FV) -
Cash Flow Analysis HP 9815A
Net present value (NPV) -
Internal rate of return (IRR) -
Amortization HP 9815A
Accumulated Interest (ACC INT) -
Balance (BAL) -
Depreciation HP 9815A
Straight line (SL) -
Sum of the years digits (SOYD) -
Declining balance (DB) -
Bonds and calendar functions HP 9815A
Bond price -
Bond yield -
Date arithmetic / calendar functions -
Memory and Programming HP 9815A
Programming language(s) RPN
RAM / Max # of variables or addressable registers 58
Max # of program steps 472
RAM / Max vars or regs with full optional RAM 250
Max # of prog steps with full optional RAM 2008
Merged program steps  Yes
Manual register / program memory allocation  Yes
Automatic register / program memory allocation -
Overlapped register and program memory -
Continuous memory -
Flags 8
Conditional tests 3
Subroutine levels 7
Indexed looping (increment by +/- 1, end at 0) -
Indexed looping (choice of increment and end) Yes
Multiple index / loop registers Yes
Line number addressing Yes
Branching by relative line number -
Global program label addressing Yes
Local program label addressing -
Indirect / computed addressing and control Yes
Multiple indirection registers Yes
Pause Yes
Alpha messages and prompts in programs On printer
Alpha program listings Yes
Alpha string manipulation -
Program step insert / delete Yes
I/O and Expansion Features HP 9815A
ROM modules -
RAM modules or expansion option Yes
General expansion slots / connector Yes*
Magnetic card reader/writer -
Tape drive Yes
Disk drive -
Upgradeable firmware -
Optical wand -
Serial port -
Infrared input -
Infrared output -
Printer Yes
Networking HP-IB Option
Other Digitizer,
2 paper tape readers,
tape punch,
pagewidth printer,
General HP 9815A
Sounds -
Self test -
Hard case (in addition to soft case) Yes
Additional Features -
Batteries -
Length (inches) 13.5"
Width 13.75"
Height 4.1"
Weight (oz or lbs) 12 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.
HP 9815A notes:
  • ENGineering format was called SCI 3.
  • IO channels (Option 002) needed to be added to allow the calculator to control peripherals. (These were standard on the 9815S.)
  • Unusual For / Next looping system using two or three registers for loop control.
  • The HP 9815S is listed on its own features page. (256/3800, 2 IO channels)
  • No pacs are included above so far.

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