HP Calculator History - The HP-45

by Wlodek Mier-Jedrzejowicz Ph.D.


Introduced on May 1 1973, this was the third handheld electronic calculator sold by HP, and the second scientific model. It built on the success of the HP-35, adding many new features. Some were taken from the HP-80, others were completely new, including the LAST X command, numbered data registers, store and recall register arithmetic, built-in conversion constants, and selection of trigonometric modes (DEG, RAD, GRAD).

It is the first handheld known to have had a code name - "Wizard". Early models had a built-in timer
mode which could be accessed by bouncing the HP-45 on a springy mattress (!) or by pressing the RCL key and then pressing CHS, 7 and 8 all at once. This would start the timer, using the contents of register X as the initial time value. If your HP-45 has this mode, then while the timer mode is selected, you can press CHS to start or stop the timer, ENTER to quit the timer and clear the display, and . to quit and leave the time in the display. Keys 1-9 store the current time in the numbered register if the timer is running, or recall the time from that register if the timer is stopped. CLX resets the timer to zero, EEX turns the display of hundredths of a second on or off, and E+ stops the timer. This timer was originally designed for use in the HP-45, but needed a crystal oscillator to provide sufficient accuracy. In the end, the crystal was left out of the HP-45, but early models still had the software built in, though it was not very accurate. The timer was later built into the HP-55.

The HP-45 is a favourite among collectors; especially HP-45s with the timer. There was a large desktop version of the HP-45, with a built-in printer, called the HP-46.


This article is part of the WMJARTS file. This file contains a series of articles written by Wlodek Mier-Jedrzejowicz and published in DATAFILE, the journal of the HPCC. The article was reproduced with permission of the author.

Copyright Wlodek Mier-Jedrzejowicz Ph.D.