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Floating Point Representation of Numbers 
Numerical inaccuracy in mathematical computations stems from the need to represent real numbers in floating point format. 
In floating point format, a fixed number of bits of storage are used to hold the sign, mantissa, and exponent of a real number, usually in base 2. 
In IEEE standard floating point on a 32 bit computer, a double precision
number consists of

Some numbers, called machine numbers, can be exactly represented in floating point. Others can't and must be rounded to the nearest machine number, introducing a small error. 