C 语言中的浮点数

float point storage layout

http://steve.hollasch.net/cgindex/coding/ieeefloat.html

Putting it All Together

So, to sum up:

1. The sign bit is 0 for positive, 1 for negative.
2. The exponent's base is two.
3. The exponent field contains 127 plus the true exponent for single-precision, or 1023 plus the true exponent for double precision.
4. The first bit of the mantissa is typically assumed to be 1.f, where f is the field of fraction bits.