> Date: Wed, 17 Oct 2001 15:22:26 -0400
> From: Bob Cohen <[log in to unmask]>
> At 02:38 PM 10/17/01 +0200, you wrote:
> (I've always assumed Double Precision meant ~ 16 digits of accuracy.
If a word of 32 bits is used for single precision,
then double precision uses 64 bits.
In those 32 or 64 bits, an exponent is stored as well as the mantissa (or
significand).
In some systems, the exponent takes 8 bits, with an effective mantissa
of 21 bits for single precision and 53 bits for double precision.
Thus single precision is about 6 decimal digits and double precision is about
16 decimal digits (on those systems).
But there have been other word sizes over the years -- including
36 bits and 60 bits, with 72 and 120 bits being used for double precision
respectively.
> It
> was quite upsetting to learn that a Lotus Spreadsheet could do it just
> fine. I believe that the spreadsheet has 18 digits of precision. I
> could have used 128 bit reals at that time.
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