Thread: what is excess in floating point format

  1. #1
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    what is excess in floating point format

    In a floating point format, why is an "excess" used?

  2. #2
    ATH0 quzah's Avatar
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    When there's too much?

    Quzah.
    Hope is the first step on the road to disappointment.

  3. #3
    Registered User
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    Do it yourself:
    Code:
    #include<stdio.h>
    
    int main(){
    	const int lfloat=0x7f7fffff;//max positive float in hex, 8 bit for expoent
    	const unsigned __int64 ldouble=0x7fefffffffffffff;//max positive double in hex, 11 bit for expoent
    
    	const float FMAX = *(const float*)&lfloat;
    	const double DMAX = *(const double*)&ldouble;
    
    	printf("FLOAT MAX: %f\nDOUBLE MAX: %lf\n",FMAX,DMAX);
    	return 0;
    }
    /******************
    
    OUTPUT
    FLOAT MAX: 340282346638528860000000000000000000000.000000
    DOUBLE MAX: 17976931348623157000000000000000000000000000000000000000000000000000
    00000000000000000000000000000000000000000000000000000000000000000000000000000000
    00000000000000000000000000000000000000000000000000000000000000000000000000000000
    00000000000000000000000000000000000000000000000000000000000000000000000000000000
    0.000000
    *******************/
    1# Me thinks C++ currently doesn't suport by the standard 64bits ints
    2# __int64 is Microsofts compiler specific keyword. Use long long int for gcc. For Borland... I don't know.
    3# Raw C and pointer casting, anyone??
    4# Explicit hex values CANNOT be assigned to floating point numbers, so I used ints as auxiliaries
    5# To understand the hex values I assigned read this article from ieee about floating point number arithmetic.
    6# When all bits from the expoent are set, the number represents then not the number it suposed to be, but "NotANumber" or "Infinity". Overflow, division by zero, who knows?

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