HP·38E/38C - Slide Rule Museum

22 Using Your Calculator
LAST X
In addition to the automatic memory stack, the HP-38E contains a
separate automatic register called the LAST X register. This register
preserves the value that was in the display before the performance of a
function. To place the contents of the LAST X register into the display
again, press []J I LAST X I
The I LAST X I key makes it easy to recover from keystroke mistakes, such
as pressing the wrong function key or keying in the wrong number. This
ease of recovery becomes especially important when you are dealing
with large numbers, where reentering may be cumbersome.
Example: Divide $55,499,041 by $7,472 after you have mistakenly
divided by $ 1,472.
Keystrokes
55499041 I ENTER. I
14728
[]J I LAST X I
8]
7472 8
Display
55,499,041.00
37,703.15
1,472.00
55,499,041.00
7,427.60
The Hidden Function (Mantissa)
Oops! You made a mistake.
Retrieves that last entry.
You're back at the
beginning.
The correct answer.
When in any display format, you wish to view the contents of the
true mantissa (all 10 digits) press [IJ CLEAR I PREFIX I and hold down
the I PREFIX I key. All 10 digits of the mantissa held internally will be
displayed. Release the key and the display will revert back to its original
contents. For more information on display formatting, refer to The
Display and Memory in Your HP Financial Calculator.
With the data intact from the last example and 7,427.60 still in the
display, use the hidden mantissa function to see the rest of the number
(hidden digits) held internally.
KeystrOkes
[IJ CLEAR I PREFIX I
Display
7427601847 Mantissa.
Even though the display returns to 7,427.60, the calculator computes
using all 10 digits of the number 7,427.601847.