Decimal and, only the best mathematicians were able to multiply or divide large numbers. These difficulties were completely solved with the introduction of the Hindu–Arabic numeral system for representing integers. This system has been extended to represent some non-integer numbers, called "decimal fractions" or "decimal numbers" for forming the "decimal numeral system". For writing numbers, the decimal system uses ten decimal digits, a decimal mark, and, for negative numbers, a minus sign "−". The decimal digits are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9; the decimal separator is the dot "" in many countries (including English speaking ones),
Decimal but may be a comma "" in other countries (mainly in Europe). For representing a nonnegative number, a decimal consists of It is generally assumed that, if , the first digit is not zero, but, in some circumstances, it may be useful to have one or more 0's on the left. This does not change the value represented by the decimal. For example, . Similarly, if , it may be removed, and conversely, trailing zeros may be added without changing the represented number. For example, and . sometimes, the unnecessary zeros are used for indicating the accuracy of a measurement.