HP-45

{{Use dmy dates|date=April 2019|cs1-dates=y}}

{{Infobox Calculator

| name = HP-45

| image = HP-45.jpg

| caption = HP-45
Advanced Scientific Electronic Pocket Calculator

| type = Scientific

| entry = RPN

| introduced = 1973

| discontinued = 1976

| processor =

| display_type = Red LED seven-segment display

| display_size = 15 digits (decimal point uses one digit), (±10^±99)

| prog_lang = RPN key stroke

| memory_data = Four-register operational stack with nine addressable memory registers + LASTx register

| memory_step =

| supply = Internal rechargeable battery or 115/230 V AC, 5 W

| weight = Calculator: {{convert|9|oz|g|abbr=on}},
recharger: {{convert|5|oz|g|abbr=on}}

| dimensions = Length: {{convert|5.8|in|mm}},
width: {{convert|3.2|in|mm}},
height: {{convert|0.7|–|1.3|in|mm}}

}}

The HP-45 is the second scientific pocket calculator introduced by Hewlett-Packard, adding to the features of the HP-35. It was introduced in 1973{{cite web |url=http://www.hp.com/hpinfo/abouthp/histnfacts/museum/personalsystems/0040/index.html |title=HP Virtual Museum: Hewlett-Packard-45 advanced scientific pocket calculator, 1973 |access-date=2017-10-15}} with an MSRP of US$395{{Cite web |url={{Google books|1T4ORu6EICkC|page=124|plainurl=yes}} |title=Those incredible new scientific pocket calculators |last=Free |first=John R. |page=124 |magazine=Popular Science |date=April 1974 |access-date=2017-10-15}} ({{Inflation|US|395|1973|fmt=eq}}).{{Inflation-fn|US}} Especially noteworthy was its pioneering addition of a shift key that gave other keys alternate functions.

The calculator was code-named Wizard,{{cite web | author-first=Włodzimierz "Włodek" Anthony Christopher |author-last=Mier-Jędrzejowicz | title=THE HP-45 | website=HP CALCULATOR HISTORY | url=https://www.xnumber.com/xnumber/WMJ_hp45.htm}} which is the first known use of a code name for a calculator.

It also contained an Easter egg that allowed users to access a not-especially accurate stopwatch mode.{{cite web | last=Miller | first=Paul E. | title=HP-45 Calculator As A Stopwatch | website=Decode Systems | date=2016-08-31 | url=http://www.decodesystems.com/hp45-stopwatch.html}}{{cite AV media|title=HP 45 Scientific Calculator Hidden Timer |url=https://www.youtube.com/watch?v=4TFV-zOzbd4 |language=en |access-date=2022-08-05 |via=youtube.com}} An accurate version of the stopwatch mode was officially featured in the 1975 successor of the HP-45, the HP-55.

File:HP-45 (101587990).jpg

The display of the HP-45 hidden timer showing 00 hours 00 minutes 07 seconds and 58/100 second.

class="wikitable" style="text-align:left" ! colspan=2 | HP-45 functions
Arithmetic	+, −, ×, ÷
Trigonometry	sin, arc sin; cos, arc cos; tan, arc tan (decimal degrees, radians or grads).
Logarithms	log10x, 10x; logex, ex
Conversions	Decimal degrees, radians or grads ↔ degrees–min.–sec. Rectangular coordinates ↔ polar coordinates. Conversion units: cm/in, kg/lb, ltr/gal
Other	1/x, √x, x2, yx, n!, %, Δ%, {{pi}}, vector arithmetic, register arithmetic. Statistical accumulation with mean and standard deviation calculations. Fixed point and scientific display modes, 0 – 9 decimal places round-off.