I tried resetting HP48S based on opinions from Mr.Rysgaard via comment. On the contrary, I hadn't known the reset switch exists from the very beginning.
So I had to find the reset switch out. Also I used web search-engine, finally I got information about the reset switch. The reset switch was located at inside of a top-right rubber feet. I felt it was very special location.
Be that as it may. I pushed it few seconds several times. But nothing improved...
I seem that an on-board battery for backing up memory had been dead or something like that, because I had not turned it on over 5 years.
...With such thoughts running through my mind, I operated a Mac OS X calculator without any purpose. Then I found out interesting function of the Mac OS X calculator.
I clicked the key-pad in the following order.
Also I was thought that this key order will be parsed as the following formula. (This is normal calculator) But the Mac OS X calculator displayed 31. This means that the Mac OS X calculator performs mathematical calculations.
I felt it was interesting, so I tested the same method with the Windows calculator. Then it became an interesting result.
I report as follows.

• Windows calculator (normal mode)
  (5 * 2 + 7) * 3 = 51
• Windows calculator (scientific mode)
  5 * 2 + 7 * 3 = 31
  
  
• Mac OS X calculator (normal mode)
  5 * 2 + 7 * 3 = 31
• Mac OS X calculator (scientific mode)
  5 * 2 + 7 * 3 = 31
• Mac OS X calculator (programmer mode)
  5 * 2 + 7 * 3 = 31

The calculation result is depending on the mode with the Windows calculator! while on the other hand, my Mac OS X calculator is so smart!
During testing like this, I found out more big feature is implemented on Mac OS X calculator. The Mac OS X calculator had been supporting RPN! (PRN menu had been existing!)
I didn't realize that... What should I do?
(to be continued)

tag : calculator