Fixed-point arithmetic

Article summary

In computing, fixed-point is a method of representing fractional (non-integer) numbers by storing a fixed number of digits of their fractional part. Dollar amounts, for example, are often stored with exactly two fractional digits, representing the cents (1/100 of a dollar). More generally, the term may refer to representing fractional values as integer multiples of some fixed small unit, e.g., a fractional amount of hours as an integer multiple of ten-minute intervals. Fixed-point number representation is often contrasted to the more complicated and computationally demanding floating-point representation. In the fixed-point representation, the fraction is often expressed in the same number base as the integer part, but using negative powers of the base b. The most common variants are decimal (base 10) and binary (base 2). The latter is commonly known also as binary scaling. Thus, if n fraction digits are stored, the value will always be an integer multiple of b −n . Fixed-point representation can also be used to omit the low-order digits of integer values, for instance, when representing large dollar values as multiples of $1000 ($1K). When decimal fixed-point numbers are displayed for human reading, the fraction digits are usually separated from those of the integer part by a radix character (usually "." in English, but "," or some other symbol in many other languages).…

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