The HP-45 was HP’s second scientific handheld electronic calculator. It added many features, including numbered data registers, store and recall register arithmetic, built-in conversion constants and selection of trigonometric modes. The HP-45 was HP's first scientific calculator to have a shift key. This was such a novel feature at the time that HP credited the key with nearly doubling the computational power of the calculator. The HP-45 added the ability to do trig functions in Radians or Grads, polar to rectangular conversions, decimal degrees to/from degrees minutes seconds, basic statistics %, % change, n! etc. It was also the first pocket calculator, to have 9 storage registers in addition to the 4 level stack. The HP-45 also added 10^x and replaced x^y with y^x. It also added the now ubiquitous Last X key and x^2. The latter was placed on an unshifted key where it makes sense. (So it actually takes one less keystroke to do x^2 than Enter, multiply.) Another feature added on the HP-45, was the formatted display. It added both fixed and scientific displays with a choice of the number of digits displayed.
The HP-45 had code to implement a timer. This was never exposed as a user feature because the lack of a quartz crystal in the HP-45 made the timer fairly inaccurate. The timer could be invoked by pressing RCL and then pressing CHS 7 8 all at the same time. Once in timer mode, CHS toggled it between running and stopped. Pressing 1-9 stored the current time in that register when the timer was running or recalled the stored time when the timer was stopped. Pressing the decimal point key, brought the calculator back to normal mode with the time still in the display. (Pressing Enter also resumed normal mode but cleared the display.)
HP-45 CALCULATOR & ACCESSORIES DETAILED CONDITION:
HP-45 CALCULATOR