Data types and formats
Singleprecision
Singleprecision floating point numbers have the following format:
31

30

23

22

0

SIGN

EXPONENT

FRACTION




^





binary point


Field

Position

Full Name

sign

31

sign bit (0==positive, 1==negative)

exponent

3023

exponent (biased by 127)

fraction

220

fraction (bits to right of binary point)

Doubleprecision
Doubleprecision floating point numbers have the following format:
63

62

52

51

0

SIGN

EXPONENT

FRACTION




^





binary point


Field

Position

Full Name

sign

63

sign bit (0==positive, 1==negative)

exponent

6252

exponent (biased by 1023)

fraction

510

fraction (bits to right of binary point)

NOTE:
For bigendian machines, the highorder word is at the low address;
for littleendian machines,
the highorder word is at the high address:
Extendedprecision
Extendedprecision floating point numbers have the following format
on the Intel386 microprocessor:
79

78

64

63

0

SIGN

EXPONENT

FRACTION




^





binary point


For extended precision, bit 63 is always a 1, and the decimal
point comes after this bit.
The other formats have an
implicit bit 1 before the fraction, as explained in
``Normalized numbers''.
Field

Position

Full Name

sign

79

sign bit (0==positive, 1==negative)

exponent

7864

exponent (biased by 16,383)

fraction

630

fraction (bit 63=1, followed by the



decimal point. Bits 620 are the fraction.

Next topic:
Normalized numbers
Previous topic:
IEEE arithmetic
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