Thread: Float Data Type Ranges

  1. #1
    Registered User
    Join Date
    Dec 2010

    Float Data Type Ranges

    First of all I want to show my source:

    Data Type Ranges (C++)

    I am trying to figure out ranges.

    A float's model


    For a float:

    1 bit for sign (a)
    8 bits for bias (b)
    23 bits for mantissa (c)

    The range for the bias: [-127,128]

    The maximum point for the term has c

    Min:2^-127 ~= -5.877e-39
    Max:2^128 ~= 3.4e38

    For term b:

    The mantissa is that:

    bmax== 2^1-2^-8~=2

    Then isn't the range of the float that one?


    1. It seems like they have ignored the value of 128 for the bias. Are they right?
    2. It seems they have also ignored the negative values. Cannot we use negative floats? It seems I can.
    Last edited by GokhanK; 02-25-2011 at 09:27 PM.

  2. #2
    and the hat of int overfl Salem's Avatar
    Join Date
    Aug 2001
    The edge of the known universe
    The very ends of the exponent are reserved for things like NaN's and infinities.
    Does this help?
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.

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