Features in optional ROMs are listed as Option. 

Display and Keyboard  HP27S 
Display type  LCD 
Display format  2 Line 
FIXed number format  Yes 
SCIentific number format  Yes 
ENGineering number format  Yes 
STanDard / ALL number format  Yes* 
Alpha messages and prompts  Yes 
Softkeys labeled by mag. card or overlay   
Softkeys labeled by display menus  Yes 
Softkeys with neither labeling system   
Status annunciators  Yes 
Redefinable keyboard   
Logic  HP27S 
Logic system  Algebraic 
Stack levels  4* 
Last x  Yes* 
Undo   
Precedence  Yes 
Parentheses  Yes 
Storage Addition (STO +)  Yes 
Storage Arithmetic (STO +, , ×, ÷)  Yes 
Storage Exponentiation (STO ^)  Yes 
Recall Arithmetic   
Named variables   
Multiple data types   
Directories   
Math  HP27S 
+, , ×, ÷  Yes 
1/x  Yes 
sq. root  Yes 
x^{2}  Yes 
LOG x  Yes 
10^{x}  Yes 
LN x  Yes 
e^{x}  Yes 
y^{x}  Yes 
pi  Yes 
%  Yes 
% change  Yes 
INTeger truncation and ABSolute value  Yes 
Trigonometric functions (SIN, COS etc.)  Yes 
Hyperbolic trig. (SINH, COSH etc.)  Yes 
# of trig. modes (degrees, radians, grads)  2 
Advanced Math  HP27S 
Solver / root finder  Yes 
Numeric integration   
Complex numbers   
Matrix operations   
Matrix writer   
Equation writer   
Symbolic operations   
Fractions   
Plotting and graphics (display)   
Plotting and graphics (printer / plotter)   
Statistical  HP27S 
Mean, standard deviation (# of variables)  2 
Summation of n, x, x^{2}  Yes 
Summation of n, x, x^{2}, y  Yes 
Summation of n, x, x^{2}, y, xy  Yes 
Summation of n, x, x^{2}, y, y^{2}, xy  Yes 
Summation of lists  Yes 
Random number generator  Yes 
Linear regression, estimate  Yes 
Curve fitting  Yes 
Correlation coefficient  Yes 
Normal distribution   
Factorial  Yes 
Gamma   
Combinations and permutations  Yes 
Scientific and Time  
Polar / rectangular conversions  Yes 
Base conversions (2, 8, 10, 16)  Yes 
Arithmetic in bases 2, 8 and 16  Yes 
Bit operations (AND, OR, XOR, ...)   
Selectable word size (164 bits)   
Selectable complement mode (1's, 2's, unsigned)   
Decimal hrs / hrs.min.sec. conversions  Yes 
Hrs.min.sec arithmetic   
Time of day clock  Yes 
Timer   
Dynamic calculations (timer × rate)   
Alarms  Yes 
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  HP27S 
Number of payments (n)  Yes 
Interest rate (i)  Yes 
Present Value (PV)  Yes 
Payment (PMT)  Yes 
Future Value (FV)  Yes 
Cash Flow Analysis  HP27S 
Net present value (NPV)   
Internal rate of return (IRR)   
Amortization  HP27S 
Accumulated Interest (ACC INT)  Yes 
Balance (BAL)  Yes 
Depreciation  HP27S 
Straight line (SL)   
Sum of the years digits (SOYD)   
Declining balance (DB)   
Bonds and calendar functions  HP27S 
Bond price   
Bond yield   
Date arithmetic / calendar functions  Yes 
Memory and Programming  HP27S 
Programming language(s)   
RAM / Max # of variables or addressable registers  6.7K bytes / 10 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  Yes 
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  HP27S 
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  Yes 
Printer  Option 
Networking   
Other   
General  HP27S 
Sounds  Yes 
Self test   
Hard case (in addition to soft case)   
Additional Features   
Batteries  3 SR 44 
Length (inches)  5.85" 
Width  3.15" 
Height  0.6" 
Weight (oz or lbs)  5 oz 
Year of introduction  1988 
Features in optional ROMs are listed as Option. 
HP27S notes:

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