Hello
I've a question for 8087 co processor
I've real number in 'x'(DQ)
I want to display this number in form of
"mantissa * 10^(exponents)"
of course, 1 <= mantissa < 10
1st. I tried to get exponent
FLD1 (load 1)
FLD x (load x)
FYL2X (ST(0)=log_2 x)
FLDLG2 (load log_10 2)
FMUL ((log_2 x)*(log_10 2) = log_10 x = st(0))
FWAIT
FIST n (store exponents in 'n')
(because log_10 x = log_10 (mantissa) + exponents,
and 0 <= log_10 (mantissa) < 1,
so FIST get integer(exponent) part)
FISUB n (log_10 - n = log_10 (mantissa))
so I can get exponents in 'n',
but mantissa is still in ST(0), in the form of
'log_10 (mantissa)'
if there is a command which can calculate 10^ST(0),
10^(log_10 (mantissa))=mantissa, but I couldn't find
such command in 8087
only F2XM1 (which calculate '2^(ST(0)) - 1') exist,
so from 2^((log_10 x) * (log_2 10)) = 2^(log_2 x) = x,
BUT, there is a problem, "F2XM1 only calculate in the
case of -1.0 <= ST(0) <= 1.0"
so I couldn't get mantissa
please help me.
Thank you

It is a long time since I wrote for the 8087.
If it helps at all, you can always put a copro
register in a ten-byte piece of memory, by
using FST or FSTP, which will let you work
separately on:
1-bit sign (high in the structure)
15-bit exponent
64-bit mantissa (lowest in the structure).