**GNU Emacs Calc 2.02 Manual**

### 3.7.9 Modes Tutorial Exercise 2

If the radix is 15 or higher, we can't use the letter ``e'` to mark
the exponent because ``e'` is interpreted as a digit. When Calc
needs to display scientific notation in a high radix, it writes
``16#F.E8F*16.^15'`. You can enter a number like this as an
algebraic entry. Also, pressing `e` without any digits before it
normally types `1e`, but in a high radix it types `16.^` and
puts you in algebraic entry: `16#f.e8f RET e 15 RET *` is another
way to enter this number.

The reason Calc puts a decimal point in the ``16.^'` is to prevent
huge integers from being generated if the exponent is large (consider
``16#1.23*16^1000'`, where we compute ``16^1000'` as a giant
exact integer and then throw away most of the digits when we multiply
it by the floating-point ``16#1.23'`). While this wouldn't normally
matter for display purposes, it could give you a nasty surprise if you
copied that number into a file and later moved it back into Calc.