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My calculator WristApps currently use "S16E7" floating point numbers which are accurate to 4 decimal places and have a range of ~3*10^7. 

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S16E7 appears to be used mainly in video cards.  It means 1 bit for sign (S), 16 bits for the mantissa, and 7 bits for the exponent (E).

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Since S16E7 is not an IEEE standard, there are probably some variations in format.  I'm using a biased exponent (the real exponent is 63 decimal less than as stored) and an unpacked mantissa (the leading 1 in the mantissa is often used for something else since it is assumed to always be a 1, but I'm not doing that to make my programs smaller).

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Convert an IEEE-754 32-bit float in hex to an S16E7 float in hex (and back again):

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  IEEE-754 HEX                                                                                         S16E7 HEX

       

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Use this page to convert between decimal numbers and IEEE-754 hex:   

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Decimal to IEEE-754:  http://babbage.cs.qc.edu/courses/cs341/IEEE-754.html

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IEEE-754 to Decimal:  http://babbage.cs.qc.edu/courses/cs341/IEEE-754hex32.html

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IEEE-754 Floating Point Math

bullet http://stevehollasch.com/cgindex/coding/ieeefloat.html
bullet http://www.cs.umd.edu/class/spring2003/cmsc311/Notes/Data/float.html
bullet http://www.apropos-logic.com/nc/FPFormats.html
bullet http://www.rit.edu/~meseec/eecc250-winter99/
bullet http://www.rit.edu/~meseec/eecc250-winter99/IEEE-754.html
bullet http://www.rit.edu/~meseec/eecc250-winter99/IEEE-754hex32.html
bullet http://www.rit.edu/~meseec/eecc250-winter99/IEEE-754references.html
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Copyright 2001  Raymond J. Allen