## Monday, May 9, 2022

### Retro Review: Hewlett Packard HP 45

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

* 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.

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

All original content copyright, © 2011-2022.  Edward Shore.   Unauthorized use and/or unauthorized distribution for commercial purposes without express and written permission from the author is strictly prohibited.  This blog entry may be distributed for noncommercial purposes, provided that full credit is given to the author.

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