Retro Review: Hewlett Packard HP 45
Quick Facts:
Model: HP 45
Company: Hewlett Packard
Years: 1973-1976
Type: Scientific
Batteries: (original) HP Battery Pack 82001A (rechargeable), compatible batteries can be found on eBay, AC Adapter 82002A
Operating Mode: RPN
Memory Registers: 9 (R1 - R9), some are used in statistics
Undocumented (by the manual) Feature: Stopwatch
Original Price: $395.00 (US)
Package Includes AC Adapter, User Manual, Pocket Guide, Carrying Case
Features - History
The HP 45 is the second scientific calculator by Hewlett Packard, first brought to the market in 1973; after the legendary HP 35 was released in 1972. The HP 45 is the second Hewlett Packard calculator to feature a shift key, after HP's first financial calculator, the HP 80.
The HP 45 operates on Reverse Polar Notation (RPN). Here is a Wikipedia page on RPN: https://en.wikipedia.org/wiki/Reverse_Polish_notation
The HP 45 added more functions to the HP 35, which features include:
* trigonometric functions and inverses
* logarithms and antilogs
* powers and roots
* fixed and scientific
* factorial of integers
* polar/rectangular conversions
* degrees/degree-minute-second conversions (DD.MMSSSS)
* percent and percent change
* three angle modes: degree, radians, grads
* Last x
* three unit conversions
* statistics
* storage and recall arithmetic
When the HP 45 is powered on, the calculator will be in FIX 2 mode.
Factorial of Integers: The function n! allows only integers from 0 to 69. It will be later HP calculators to extend the factorial function to the real numbers.
Polar and Rectangular Conversions: The conversions involve the X and Y stack. In polar form, X represents r and Y represents θ.
Conversions: The HP 45 provides conversion factors for unit conversions. Examples provided in FIX 2 mode.
[ shift ] [ 7 ]: cm/in. 1 in = 2.54 cm.
18 in to cm: 18 [ shift ] [ 7 ] [ × ] returns 45.72 cm
50 cm to in: 50 [ shift ] [ 7 ] [ ÷ ] returns 19.69 ft
[ shift ] [ 8 ]: kg/lb. 1 lb ≈ .4536 kg
200 lb to kg: 200 [ shift ] [ 8 ] [ × ] returns 90.72 kg
66.5 kg to lb: 66.5 [ shift ] [ 8 ] [ ÷ ] returns 146.61 lb
[ shift ] [ 9 ]: ltr/gal. 1 gal ≈ 3.7854 ltr
150 gal to ltr: 150 [ shift ] [ 9 ] [ × ] returns 567.81ltr
690 ltr to gal: 690 [ shift ] [ 9 ] [ ÷ ] returns 182.28 gal
Percent: The [ % ] key returns x% of y, while leaving the value in the Y stack. This could be followed up with [ + ] or [ - ] for percent adding and subtracting calculations.
Add 6% to 150.
150 [ ENTER ] 6 [ % ] [ + ] returns 159.00
Percent Change: The [ shift ] [ % ] (∆%) calculates percent change: (y - x)/y * 100 with the value of the Y stack remains. y is old, x is new.
What is the percent change from 35 to 45?
35 [ ENTER ] 45 [ shift ] [ % ] returns 28.57 (%)
The HP 45 has storage and recall arithmetic for the four arithmetic functions (+, -, ×, ÷). I love storage arithmetic and any time we get recall arithmetic, it's a huge bonus.
The keyboard feels good and the keys feel responsive.
Statistics
The HP 45 has one-variable statistics, which some sums for y-data.
R5 = n
R6 = Σx^2
R7 = Σx
R8 = Σy
RCL Σ+ returns Σx to the X stack and Σy to the Y stack
[ shift ] [ R↓ ] returns x-bar to the X stack and sx to the Y stack
Stopwatch
A famous and undocumented feature of the HP 45 is a stopwatch. The stopwatch is accessed by the sequence [ RCL ] then pressing [ 7 ], [ 8 ], and [ CHS ] keys at the same time. Done right the display will be in the form:
hh.mm ss 'ss
Press [ CHS ] to start and stop the timer, and any number keys can be used to store the time for lap records. The stored time will be stored as a decimal and the two two digit exponent will store the hundredths of seconds.
Pressing [ CLx ] clears the time and [ ENTER ] returns us to the operator mode. I understand that due to the lack of crystal, the timer is somewhat inaccurate.
Closing Thoughts
I love this calculator! It's good to have a calculator from the 1970s, especially from HP.
Until next time,
Eddie
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