Exceptional Values (Sun WorkShop Compiler C 5.0 User's Guide)

Sun WorkShop Compiler C 5.0 User's Guide

Exceptional Values

float and double numbers are said to contain a "hidden," or implied, bit, providing for one more bit of precision than would otherwise be the case. In the case of long double, the leading bit is implicit (SPARC) or explicit (Intel); this bit is 1 for normal numbers, and 0 for subnormal numbers.

Table A-10 float Representations


normal number (0<e<255):	(`-1`)^Sign2 ^{(exponent - 127)}1.`f`
subnormal number (e=0, f!=0):	(`-1`)^Sign2 ^(-126)0.`f`
zero (e=0, f=0):	(`-1`)^Sig`n`0.0
signaling NaN	s=u, e=255(max); f=.0uuu-uu; at least one bit must be nonzero
quiet NaN	s=u, e=255(max); f=.1uuu-uu
Infinity	s=u, e=255(max); f=.0000-00 (all zeroes)

Table A-11 double Representations


normal number (0<e<2047):	(`-1`)^Sign2 ^{(exponent - 1023)}1.`f`
subnormal number (e=0, f!=0):	(`-1`)^Sign2 ^(-1022)0.`f`
zero (e=0, f=0):	(`-1`)^Sign0.0
signaling NaN	s=u, e=2047(max); f=.0uuu-uu; at least one bit must be nonzero
quiet NaN	s=u, e=2047(max); f=.1uuu-uu
Infinity	s=u, e=2047(max); f=.0000-00 (all zeroes)

Table A-12 long double Representations


normal number (0<e<32767):	(`-1`)^Sign2 ^{(exponent - 16383)}1.`f`
subnormal number (e=0, f!=0):	(`-1`)^Sign2 ^(-16382)0.`f`
zero (e=0, f=0):	(`-1`)^Sign0.0
signaling NaN	s=u, e=32767(max); f=.0uuu-uu; at least one bit must be nonzero
quiet NaN	s=u, e=32767(max); f=.1uuu-uu
Infinity	s=u, e=32767(max); f=.0000-00 (all zeroes)