The Museum of HP Calculators

HP 9820 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 9820
Display type LED
Display format 1 16 char line
FIXed number format Yes
SCIentific number format Yes
ENGineering number format -
STanDard / ALL number format -
Alpha messages and prompts Yes
Softkeys labeled by mag. card or overlay Yes
Softkeys labeled by display menus -
Softkeys with neither labeling system -
Status annunciators -
Redefinable keyboard -
Logic HP 9820
Logic system Algebraic
Stack levels -
Last x -
Undo -
Precedence Yes
Parentheses Yes
Storage Addition (STO +) Yes
Storage Arithmetic (STO +, −, ×, ÷) Yes
Storage Exponentiation (STO ^) -
Recall Arithmetic -
Named variables Limited*
Multiple data types -
Directories -
Math HP 9820
+, −, ×, ÷ Yes 
1/x -
x2 -
LOG x Option
10x Option
LN x Option
ex Option
yx Option
π Option
% -
% change -
INTeger truncation and ABSolute value Option
Trigonometric functions (SIN, COS etc.) Option
Hyperbolic trig. (SINH, COSH etc.) -
# of trig. modes (degrees, radians, grads) 3 (option)
Advanced Math HP 9820
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) Option
Statistical HP 9820
Mean, standard deviation (# of variables) -
Σ of n, x, x2 -
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 9820
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 9820
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 9820
Number of payments (n) -
Interest rate (i) -
Present Value (PV) -
Payment (PMT) -
Future Value (FV) -
Cash Flow Analysis HP 9820
Net present value (NPV) -
Internal rate of return (IRR) -
Amortization HP 9820
Accumulated Interest (ACC INT) -
Balance (BAL) -
Depreciation HP 9820
Straight line (SL) -
Sum of the years digits (SOYD) -
Declining balance (DB) -
Bonds and calendar functions HP 9820
Bond price -
Bond yield -
Date arithmetic / calendar functions -
Memory and Programming HP 9820
Programming language(s) pre HPL
RAM / Max # of variables or addressable registers 172
Max # of program steps Variable*
RAM / Max vars or regs with full optional RAM 428
Max # of prog steps with full optional RAM Variable*
Merged program steps  Highly
Manual register / program memory allocation  -
Automatic register / program memory allocation Yes
Overlapped register and program memory -
Continuous memory -
Flags 16
Conditional tests 4
Subroutine levels <32*
Indexed looping (increment by +/- 1, end at 0) -
Indexed looping (choice of increment and end) -
Multiple index / loop registers -
Line number addressing Yes
Branching by relative line number Yes
Global program label addressing Yes
Local program label addressing -
Indirect / computed addressing and control Yes
Multiple indirection registers Yes
Pause -
Alpha messages and prompts in programs Yes
Alpha program listings Yes
Alpha string manipulation -
Program step insert / delete Yes
I/O and Expansion Features HP 9820
ROM modules Yes
RAM modules or expansion option Yes
General expansion slots / connector Yes
Magnetic card reader/writer Yes
Tape drive Yes
Disk drive -
Upgradeable firmware -
Optical wand -
Serial port -
Infrared input -
Infrared output -
Printer Yes
Networking -
Other Digitizer,
BCD & gen I/O
optical card reader,
large display,
paper tape reader,
typewriter coupler,
General HP 9820
Sounds -
Self test -
Hard case (in addition to soft case) -
Additional Features -
Batteries -
Length (inches) 19.5"
Width 16"
Height 7"
Weight (oz or lbs) 35 lbs
Year of introduction 1972
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 9820 notes:
  • The calculator had six variables named A, B, C. X, Y, and Z. All other memory was in the form of numeric registers.
  • Memory was reallocated from registers to program as needed. Because lines where highly variable in length there is no fixed maximum # of lines, but on average, 8 keystrokes on a program line consumed one register.
  • Subroutine nesting limits were somewhat variable but limited to at most 31 levels in the basic calculator or about twice that if the User Definable Functions ROM was installed.
    Indirection was done via refering to other registers within a register reference - for example r(r(2)+r(3)) refered to the register whose number was the sum of the contents of registers 2 and 3.
  • Register r3 could be referenced as r3 or r(3). Therefore, registers could be treated as separate variables or as a single array.
  • The calculator allowed line and label addressing but only branches to labels were guaranteed to be maintained when lines were inserted or deleted.
  • Only the Math ROM and pac have been included above.

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