IEEE floating point format

Bob Knighten knighten at pinocchio
Sat Jul 29 04:05:39 AEST 1989


Single format:  Numbers in the single format are composed of three fields:
	A 1-bit sign S
	A biased exponent e = exponent + 127
	A fraction f = 0.b b ...b
                          1 2    23

The exponent range is -126 to +127.  Exponent = 128 is used to encode
+/-infinity and NaNs.  Exponent = -127 is used to encode +/-0 and denormalized
numbers.

The layout is:

	1     8             23              width
       |S|    e   |          f           |
          m      l m                    l   order

where m stands for most significant bit
and   l stands for least significant bit

 
Double format:  Numbers in the single format are composed of three fields:
	A 1-bit sign S
	A biased exponent e = exponent + 1023
	A fraction f = 0.b b ...b
                          1 2    52

The exponent range is -1022 to +1023.  Exponent = 1024 is used to encode
+/-infinity and NaNs.  Exponent = -1023 is used to encode +/-0 and denormalized
numbers.

The layout is:

     1     11                              52                            width
    |S|     e     |                         f                          |
       m         l m                                                  l  order

where m stands for most significant bit
and   l stands for least significant bit

 
The value of a number represented in either of these formats is
                S          exponent
	x = (-1)  * 1.f * 2

--
Bob Knighten                        
Encore Computer Corp.
257 Cedar Hill St.        
Marlborough, MA 01752
(508) 460-0500 ext. 2626

Internet:  knighten at encore.com
UUCP:  {bu-cs,decvax,necntc,talcott}!encore!knighten



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