Features in optional ROMs are listed as Option. 

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   
sq. root  Yes 
x^{2}   
LOG x  Option 
10^{x}  Option 
LN x  Option 
e^{x}  Option 
y^{x}  Option 
pi  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)   
Summation of n, x, x^{2}   
Summation of n, x, x^{2}, y   
Summation of n, x, x^{2}, y, xy   
Summation of n, x, x^{2}, y, y^{2}, xy   
Summation of lists   
Random number generator   
Linear regression, estimate   
Curve fitting  + 
Correlation coefficient   
Normal distribution   
Factorial   
Gamma   
Combinations and permutations   
Scientific and Time  
Polar / rectangular conversions   
Base conversions (2, 8, 10, 16)   
Arithmetic in bases 2, 8 and 16   
Bit operations (AND, OR, XOR, ...)   
Selectable word size (164 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  
Centimeters / inches   
Millimeters / inches   
Meters / feet   
Kilograms / pounds (mass)   
Newtons / pounds (force)   
British thermal units / joules   
Liters / gallons   
° Celsius / ° Fahrenheit   
Other   
Userdefined 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, plotter, BCD & gen I/O optical card reader, large display, paper tape reader, typewriter coupler, etc. 
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. 
HP 9820 notes:

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