IBM C and C++ Compilers conforms to IEEE format, in which a floating point number is represented in terms of sign (S), exponent (E), and fraction (F):
(-1)S x 2E x 1.F
| Type | double | |||||||||||||||||||||
| Alignment | ||||||||||||||||||||||
| Bit Mapping |
In the internal
representation, there is 1 bit for the sign (S), 11 bits
for the exponent (E), and 52 bits for the fraction (F).
The bits are mapped with the fraction in bit 0 to bit 51,
the exponent in bit 52 to bit 62, and the sign in bit 63:
Read the lines vertically from top to
bottom. For example, the third column of numbers shows
that bit 61 is part of the exponent. |
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| Storage Mapping |
In the following mapping,
high memory is to the right.
|
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Mapping of Fundamental Data Types
Mapping of Compound
Data Types
Format of Four-Byte
Floating Point Data
Format of Ten-Byte
Floating Point Data in Sixteen Byte Fields