The Museum of HP Calculators

Calculator Comparison

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-11C HP-15C
Display type LCD LCD
Display format 1 Line 1 Line
FIXed number format Yes Yes
SCIentific number format Yes Yes
ENGineering number format Yes Yes
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 Yes Yes
Status annunciators Yes Yes
Redefinable keyboard - -
     
Logic HP-11C HP-15C
Logic system RPN RPN
Stack levels 4 4
Last x Yes Yes
Undo - -
Precedence - -
Parentheses - -
Storage Addition (STO +) Yes Yes
Storage Arithmetic (STO +, -, ×, ÷) Yes Yes
Storage Exponentiation (STO ^) - -
Recall Arithmetic - Yes
Named variables - -
Multiple data types - -
Directories - -
     
Math HP-11C HP-15C
+, -, ×, ÷ Yes  Yes 
1/x Yes Yes
sq. root Yes Yes
x2 Yes Yes
LOG x Yes Yes
10x Yes Yes
LN x Yes Yes
ex Yes Yes
yx Yes Yes
pi Yes Yes
% Yes Yes
% change Yes Yes
INTeger truncation and ABSolute value Yes Yes
Trigonometric functions (SIN, COS etc.) Yes Yes
Hyperbolic trig. (SINH, COSH etc.) Yes Yes
# of trig. modes (degrees, radians, grads) 3 3
     
Advanced Math HP-11C HP-15C
Solver / root finder - Yes
Numeric integration - Yes
Complex numbers - Yes
Matrix operations - Yes
Matrix writer - -
Equation writer - -
Symbolic operations - -
Fractions - -
Plotting and graphics (display) - -
Plotting and graphics (printer / plotter) - -
     
Statistical HP-11C HP-15C
Mean, standard deviation (# of variables) 2 2
Summation of n, x, x2 Yes Yes
Summation of n, x, x2, y Yes Yes
Summation of n, x, x2, y, xy Yes Yes
Summation of n, x, x2, y, y2, xy Yes Yes
Summation of lists - -
Random number generator Yes Yes
Linear regression, estimate  Yes Yes
Curve fitting - -
Correlation coefficient Yes Yes
Normal distribution - -
Factorial Yes Yes
Gamma Yes Yes
Combinations and permutations Yes Yes
     
Scientific and Time

HP-11C

HP-15C

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

HP-11C

HP-15C

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-11C HP-15C
Number of payments (n) - -
Interest rate (i) - -
Present Value (PV) - -
Payment (PMT) - -
Future Value (FV) - -
     
Cash Flow Analysis HP-11C HP-15C
Net present value (NPV) - -
Internal rate of return (IRR) - -
     
Amortization HP-11C HP-15C
Accumulated Interest (ACC INT) - -
Balance (BAL) - -
     
Depreciation HP-11C HP-15C
Straight line (SL) - -
Sum of the years digits (SOYD) - -
Declining balance (DB) - -
     
Bonds and calendar functions HP-11C HP-15C
Bond price - -
Bond yield - -
Date arithmetic / calendar functions - -
     
Memory and Programming HP-11C HP-15C
Programming language(s) RPN RPN
RAM / Max # of variables or addressable registers 21 67
Max # of program steps 203 448*
RAM / Max vars or regs with full optional RAM - -
Max # of prog steps with full optional RAM - -
Merged program steps 

Yes

Yes

Manual register / program memory allocation  - Yes
Automatic register / program memory allocation

Yes

-

Overlapped register and program memory - -
Continuous memory

Yes

Yes

Flags 2 10
Conditional tests 8 12
Subroutine levels 4 7
Indexed looping (increment by +/- 1, end at 0) Yes Yes
Indexed looping (choice of increment and end) Yes Yes
Multiple index / loop registers - Loop only
Line number addressing - Via I*
Branching by relative line number - -
Global program label addressing Yes Yes
Local program label addressing - -
Indirect / computed addressing and control Yes Yes
Multiple indirection registers - -
Pause Yes Yes
Alpha messages and prompts in programs - -
Alpha program listings - -
Alpha string manipulation - -
Program step insert / delete Yes Yes
     
I/O and Expansion Features HP-11C HP-15C
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-11C HP-15C
Sounds - -
Self test Yes Yes
Hard case (in addition to soft case) - -
Additional Features - -
Batteries 3 SR44 3 SR44
Length (inches) 5.1" 5.1"
Width 3.1" 3.1"
Height 0.6" 0.6"
Weight (oz or lbs) 4 oz 4 oz
Year of introduction 1981 1982

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-11C notes:
  • Self test: with the calculator off, hold the × key and press ON. The calculator will display running for around half a minute and then activate the entire display to indicate success. The test my be done continuously by pressing + while holding the ON key. To stop the continuous test at the end of the current iteration, press and hold - and then press ON.
  • There is also a keyboard test. With the calculator off, press and hold ÷ and press ON. Now press each key from the top left moving left to right and then down (the enter key gets pressed in both the third and fourth rows.) If all keys are pressed in the correct order and are working, the model number (without the C) is displayed. Otherwise, Error 9 is displayed. (The display will show a changing pattern of segments as keys are pressed.)
HP-15C notes:
  • The HP-15C had enough memory for 448 one-byte instructions but some instructions required two bytes.
  • If the number in the I register was negative, the calculator branched to the line number indicated by the absolute value of that number.
  • Self test: with the calculator off, hold the × key and press ON. The calculator will display running for around half a minute and then activate the entire display to indicate success. The test my be done continuously by pressing + while holding the ON key. To stop the continuous test at the end of the current iteration, press and hold - and then press ON.
  • There is also a keyboard test. With the calculator off, press and hold ÷ and press ON. Now press each key from the top left moving left to right and then down (the enter key gets pressed in both the third and fourth rows.) If all keys are pressed in the correct order and are working, the model number (without the C) is displayed. Otherwise, Error 9 is displayed. (The display will show a changing pattern of segments as keys are pressed.)

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