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A repeating decimal or recurring decimal is a decimal representation of a number whose digits are eventually periodic (that is, after some place, the same sequence of digits is repeated forever); if this sequence consists only of zeros (that is if there is only a finite number of nonzero digits), the decimal is said to be terminating, and is not considered as repeating.
In this context, the usual decimals, with a finite number of non-zero digits after the decimal separator, are sometimes called terminating decimals. A repeating decimal is an infinite decimal that, after some place, repeats indefinitely the same sequence of digits (e.g., 5.123144144144144... = 5.123 144 ). [ 4 ]
Also the converse is true: The decimal expansion of a rational number is either finite, or endlessly repeating. Finite decimal representations can also be seen as a special case of infinite repeating decimal representations. For example, 36 ⁄ 25 = 1.44 = 1.4400000...; the endlessly repeated sequence is the one-digit sequence "0".
Stylistic impression of the repeating decimal 0.9999..., representing the digit 9 repeating infinitely. In mathematics, 0.999... (also written as 0. 9, 0.., or 0.(9)) is a repeating decimal that is an alternative way of writing the number 1.
For example, the decimal number 123456789 cannot be exactly represented if only eight decimal digits of precision are available (it would be rounded to one of the two straddling representable values, 12345678 × 10 1 or 12345679 × 10 1), the same applies to non-terminating digits (. 5 to be rounded to either .55555555 or .55555556).
A real number is computable if its digit sequence can be produced by some algorithm or Turing machine. The algorithm takes an integer as input and produces the -th digit of the real number's decimal expansion as output. (The decimal expansion of a only refers to the digits following the decimal point.)
Following the steps above, we can create a β-expansion for a real number (the steps are identical for an <, although n must first be multiplied by −1 to make it positive, then the result must be multiplied by −1 to make it negative again).
As an example, 9 780 657 631 has 1132 steps, as does 9 780 657 630. The starting values having the smallest total stopping time with respect to their number of digits (in base 2) are the powers of two since 2 n is halved n times to reach 1, and is never increased.