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Controlling float precision

How to control the precision of a float variable, so that it can be used for further calculations.
Example
float a=0.1033333
printf("A= %.3f",a); - will print A= 0.103, but
float b= a*1000 - in this statment i want A to use the value 0.103, instead of 0.103333,
so how to assign the precision to the variable, just not for printing it but also for using it later in the program.
Thanks

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ozo

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SOLUTION

zebada

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jmcg

You may be chasing this problem for a while. In C, you can't control the precision of a float or double variable to be different from the underlying machine representation of floating point. You can do rounding, as the sample code from ozo and zebada shows you, but on most architectures, division by powers of 10 does not give an exact result. The C libraries will provide rounding when doing formatted output of floating point, as you've already seen.

If exact control over precision is what you need, you may have to give up on using float and double data types and recode to use a fixed-precision arithmetic package. Try a search on Google for the phrase "fixed-precision arithmetic" and you'll find some starting points.

sunnycoder

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