printf () bug?

[Bill Schaffer]

Is there a printf() problem using 'long double' vs 'double' on 
Windows Xp with i386?

printf( %.20lf  %.20Lf ) for 'double' and 'long double' variables
result in both having 16-17 digits of precession.  Meaning sign 
bit & 8 bit exponent, gives 64-8-1 = 55 bits of precession.

  2^55 = 3.6 * 10^16, or about 16 digits of precession.

Printing various examples shows 16 digit accuracy both though 
'sizeof(long double)' equals 12 bytes, and 'sizeof(double)' 
equals 8.  (the '|' below indicates limit of accuracy).


sizeof()          1.6867376747234567891345 Orginal
                                  |
08 lf             1.68673767472345681462 16 digits
12 Lf             1.68673767472345681462

             161600.6867376747234567891  Orginal
                              |
08 lf        161600.68673767472500912845 17 digits
12 Lf        161600.68673767472500912845

       123456789123.123456789123  Orginal
                        |
08 lf  123456789123.12345886230468750000 17 digits
12 Lf  123456789123.12345886230468750000

      1234567891237.123456789123  Orginal
                      |
08 lf 1234567891237.12353515625000000000 16 digits
12 Lf 1234567891237.12353515625000000000

Both types print the same. It seems 'long double' should give better
precession.

Printf() problem?
or compiler load of 'long double' constant problem?
or 'long double' allocates 12 bytes but i386 handles only 8?

Or its just me.

Regards

Bill Schaffer