* Representation of "double" in powerpc
@ 2006-11-10 23:10 ramesh karra
2006-11-11 3:53 ` John (Eljay) Love-Jensen
0 siblings, 1 reply; 2+ messages in thread
From: ramesh karra @ 2006-11-10 23:10 UTC (permalink / raw)
To: gcc-help
Hi,
I would like to know how the "double" type is
represented by powerpc gcc. How many bits are
allocated for exponent and mantissa? Is the LSB the
sign bit or the MSB?
Thanks
Ramesh
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* RE: Representation of "double" in powerpc
2006-11-10 23:10 Representation of "double" in powerpc ramesh karra
@ 2006-11-11 3:53 ` John (Eljay) Love-Jensen
0 siblings, 0 replies; 2+ messages in thread
From: John (Eljay) Love-Jensen @ 2006-11-11 3:53 UTC (permalink / raw)
To: ramesh karra, gcc-help
Hi Ramesh,
The double type on PowerPC with GCC is represented in IEEE 754 fashion. 64 bits "double precision".
SXXXXXXX XXXXIMMMM MMMMMMMM MMMMMMMM MMMMMMMM MMMMMMMM MMMMMMMM MMMMMMMM
S is the 1 sign bit
X is the 11 exponent bits (+1023 biased)
I is the implied (virtual) most-significant bit for normalized numbers
M is the 52 mantissa bits
The order above is byte-by-byte from low memory address to high memory address.
HTH,
--Eljay
http://en.wikipedia.org/wiki/IEEE_754
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