DAVID G. SIMPSON

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IEEE NUMBERS

 Fortran  C (typical)  Bytes  Mant. Bits  Exp. Bits  Sig. Digits  Range 
 CHARACTER  char 
1
7
-
2.11
 127 
 INTEGER*2  short int 
2
15
-
4.52
 32,767 
 INTEGER*4  long int 
4
31
-
9.33
 2.15E+09 
 INTEGER*8  long long int 
8
63
-
18.96
 9.22E+18 
 REAL*4  float 
4
(24)
8
7.22
 1.0E±38 
 REAL*8 (D.P.)  double 
8
(53)
11
15.95
 1.0E±308 
 -  long double 
10
64
15
19.27
 1.0E±4931 
 REAL*16  - 
16
112
15
33.72
 1.0E±4931 

Notes:

  1. Where the number of mantissa bits is in parentheses, the number includes an implied initial 1 bit. The number of bits actually stored is one less than this number.
  2. The number of significant digits corresponding to b (mantissa) bits is b / log2 10 = 0.30103 b.
  3. The range of a floating-point number is approximately 22x-1, where x is the number of exponent bits. Ranges of floating-point numbers shown in the table are approximate.
  4. Each number also uses one bit for the sign of the number, so the total number of bits used is (# mantissa bits) + (# exponents bits) + (1 bit for sign). The exponent is biased, so it does not contain an explicit sign bit.

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