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HP_calcs: 45 (version-1)

...from PANDEL Ralph: This calculator has an integrated easter egg in the form of a stopwatch. The stopwatch had been planned for use in the HP: 55, but the 45 and 55 are using partially the same hardware (The stopwatch in HP 55 is working much more accurate by using an other quartz crystal). Because of this lack of accuracy, the code to this stopwatch was never exposed in the owner's manual as a user feature. The code is: shift key, clear, RCL, and then you have to press CHS and 7 and 8 simultaneously. CHS plus 4/5 or plus 1/2 do the same.