HP-42S display


I inherited an HP-42S calulator and have no manual for it.

I have been able to use it for simple math functions, which is all I require. However, all of a sudden it changed display formats and I don't know how to get it to switch back to the normal 2 line basic display??

Any help would be most appreciated.




It sounds like it's showing a menu and that's why you're only seeing X, instead of seeing both X and Y. If that is indeed the case, you can get rid of the menu by pressing EXIT; you may have to press it more than once if you're inside a nested menu.

If it's the number display format you're talking about, you can control that using the DISP menu (Shift E): FIX, followed by a two-digit number from 0 to 11, selects fixed mode, where you see a constant number of digits behind the decimal; SCI selects scientific notation, where there's always an exponent of 10, even if the number could be displayed without one; ENG, or engineering mode, is like SCI mode except the exponent is always a multiple of 3, making it easier to convert to SI-style magnitude prefixes. ALL mode is like FIX 11 but does not display trailing zeroes.


- Thomas


Hi Dick,

It sounds like your calculator is defective and should be sold to someone on the forum for $10 ;)

You can try resetting it by turning it off, then hold down the "ON" key, press and hold the E+ and XEQ buttons, then release the On button. This will erase everything in it's memory, but should bring you back to default.



What Dave describes is a RESET of your HP-42S. Think of the 3 keys in Windows d;-)

You may as well have entered complex or matrix mode. Please note scans of the original manuals are available in pdf through this museum for little money. Excellent ROI.


Please note scans of the original manuals are available in pdf through this museum for little money. Excellent ROI.

However, if you want quick and free, try this.

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