The Museum of HP Calculators

HP-65 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-65
Display type LED
Display format 1 Line
FIXed number format Yes
SCIentific number format Yes
ENGineering number format -
STanDard / ALL number format -
Alpha messages and prompts -
Softkeys labeled by mag. card or overlay Yes
Softkeys labeled by display menus -
Softkeys with neither labeling system -
Status annunciators -
Redefinable keyboard -
Logic HP-65
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-65
+, −, ×, ÷ Yes 
1/x Yes
x2 Yes
LOG x Yes
10x Yes
LN x Yes
ex Yes
yx Yes
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-65
Solver / root finder +
Numeric integration +
Complex numbers +
Matrix operations + (2×2)
Matrix writer -
Equation writer -
Symbolic operations -
Fractions -
Plotting and graphics (display) -
Plotting and graphics (printer / plotter) -
Statistical HP-65
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 Yes
Gamma -
Combinations and permutations +
Scientific and Time HP-65
Polar / rectangular conversions Yes
Base conversions (2, 8, 10, 16) Octal, +
Arithmetic in bases 2, 8 and 16 + (octal)
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 Yes
Time of day clock -
Timer -
Dynamic calculations (timer × rate) -
Alarms -
Unit Conversions HP-65
Centimeters / inches some
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-65
Number of payments (n) +
Interest rate (i) +
Present Value (PV) +
Payment (PMT) +
Future Value (FV) +
Cash Flow Analysis HP-65
Net present value (NPV) +
Internal rate of return (IRR) +
Amortization HP-65
Accumulated Interest (ACC INT) +
Balance (BAL) +
Depreciation HP-65
Straight line (SL) +
Sum of the years digits (SOYD) +
Declining balance (DB) +
Bonds and calendar functions HP-65
Bond price +
Bond yield +
Date arithmetic / calendar functions +
Memory and Programming HP-65
Programming language(s) RPN
RAM / Max # of variables or addressable registers 9 Registers
Max # of program steps 100
RAM / Max vars or regs with full optional RAM -
Max # of prog steps with full optional RAM -
Merged program steps  Partially
Manual register / program memory allocation  -
Automatic register / program memory allocation -
Overlapped register and program memory -
Continuous memory -
Flags 2
Conditional tests 4
Subroutine levels 1
Indexed looping (increment by +/- 1, end at 0) Yes
Indexed looping (choice of increment and end) -
Multiple index / loop registers -
Line number addressing -
Branching by relative line number -
Global program label addressing Yes
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 Yes
I/O and Expansion Features HP-65
ROM modules -
RAM modules or expansion option -
General expansion slots / connector -
Magnetic card reader/writer Yes
Tape drive -
Disk drive -
Upgradeable firmware -
Optical wand -
Serial port -
Infrared input -
Infrared output -
Printer -
Networking -
Other -
General HP-65
Sounds -
Self test -
Hard case (in addition to soft case) Yes
Additional Features -
Batteries Rechargeable
Length (inches) 6.0"
Width 3.2"
Height 1.4"
Weight (oz or lbs) 11 oz
Year of introduction 1974
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-65 notes:
  • The HP-65 had an unusual f-1 key, which invoked the inverse of the printed function.
  • FIX mode was set by pressing DSP . # (# was the number of desired digits)
  • SCI mode was set by pressing DSP #
  • The only looping function was DSZ, which decremented register R8 until it reached 0.
  • Register R9 was overwritten by trig functions, polar rectangular conversions. During conditional tests, R9 served as a Last x register.
  • The HP-65 powered up with programs entered to give default functions to the A-E keys (1/x etc.). They provided unshifted access to these functions when other programs weren't in use.
  • When a subroutine was called, the 65 kept track of the return address by inserting a marker instruction into the program memory. If you stopped a program while in a subroutine, you could switch to program mode, move to the return address and actually see the marker. (Which displayed as a 41 keycode - same as Enter.)
  • Medical pac has some conversions.

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