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On a seven segment display the hexadecimal characters can be displayed thusly:

 _      _   _       _   _   _   _   _   _              _   _ 
| |  |  _|  _| |_| |_  |_    | |_| |_| |_| |_   _  _| |_  |_ 
|_|  | |_   _|   |  _| |_|   | |_|  _| | | |_| |_ |_| |_  |  

Simple enough, eh?

I once ran across a microcomputer training manual, (If memory serves, it was distributed by Ampex.) that claimed the correct way to display the hexadecimal characters was as follows:

 _      _   _       _   _   _   _   _              _        
| |  |  _|  _| |_| |_  |_    | |_| |_| |_   _  _| |_ |_|   |
|_|  | |_   _|   |  _| |_|   | |_| | | |_| |_ |_| |  | | |_|

The explanation was that this eliminated the possibility of confusion when viewing an inverted display. I dismissed this as unique and amusing lore, until I encountered a customized Control Data Corporation, FDS disk drive. I needed to change a parameter on the drive and watched with amusement as I pushed the increment button and the display skipped `9' and `E' and didn't `roll over' until it incremented past `J'! Now, given that this was a 200lb. disk drive mounted in a rack, (with very specific instructions on the need for the unit to remain level during operation), I am at a loss to explain the need for this type of display. I have never seen such a display since, nor sadly, have I been able to track down that training manual again.