Отправлено Shandy 02 ноября 2006 г. 16:45 В ответ на: Чем можно заменить функцию _chkfloat_ от Keil C51? отправлено <font color=gray>ubobrov</font> 02 ноября 2006 г. 16:09

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 0by prefixing F with an implicit leading 1 and a binary point.

If E=0 and F is nonzero, then V=(-1)**S * 2 ** (-126) * (0.F) These are "unnormalized" values.

If E=0 and F is zero and S is 1, then V=-0

If E=0 and F is zero and S is 0, then V=0
In particular,
0 00000000 00000000000000000000000 = 0
1 00000000 00000000000000000000000 = -0
0 11111111 00000000000000000000000 = Infinity
1 11111111 00000000000000000000000 = -Infinity
0 11111111 00000100000000000000000 = NaN
1 11111111 00100010001001010101010 = NaN
0 10000000 00000000000000000000000 = +1 * 2**(128-127) * 1.0 = 2
0 10000001 10100000000000000000000 = +1 * 2**(129-127) * 1.101 = 6.5
1 10000001 10100000000000000000000 = -1 * 2**(129-127) * 1.101 = -6.5
0 00000001 00000000000000000000000 = +1 * 2**(1-127) * 1.0 = 2**(-126)
0 00000000 10000000000000000000000 = +1 * 2**(-126) * 0.1 = 2**(-127)
0 00000000 00000000000000000000001 = +1 * 2**(-126) *
0.00000000000000000000001 =
2**(-149) (Smallest positive value)