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Many of the numbers a computer deals with are whole numbers (integers) which can be easiy represented in binary, but real world numbers can span a huge range of sizes. Floating point is a method of representing such numbers in two parts: a mantissa represents the significant digits and an exponent tells you where the decimal point comes (or the binary point for binary numbers). This is similar to the scientific notation in which one and a half million would be written as 1.5x10⁶.