Representation of "double" in powerpc

John (Eljay) Love-Jensen eljay@adobe.com
Sat Nov 11 03:53:00 GMT 2006


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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