single precision 和 double precision float区别

Single Precision

The IEEE single precision floating point standard representation requires a 32 bit word, which may be represented as numbered from 0 to 31, left to right.

The first bit is the sign bit, S, the next eight bits are the exponent bits, ‘E’, and the final 23 bits are the fraction ‘F’:

S EEEEEEEE FFFFFFFFFFFFFFFFFFFFFFF
0 1      8 9                    31

The value V represented by the word may be determined as follows:

If E=255 and F is nonzero, then V=NaN (“Not a number”) If E=255 and F is zero and S is 1, then V=-Infinity If E=255 and F is zero and S is 0, then V=Infinity If 0