Number of base-FLT_RADIX digits in a double precision
floating-point significand.
Include
<float.h>
Value
The value 24 by
default, 53 if the switch -fno-short-double is used.
Remarks
By default, a double type is the same size as a float type (32-bit
representation). The -fno-short-double switch allows the IEEE 64-bit
representation to be used for a double precision floating-point value.