Place-value Notation
In a place value or positional notation system like Hindu-Arabic numerals, the units place is the last character (or digit) of an integral number; this is the rightmost in left-to-right writing systems like English. In such a case it has the smallest place value. It is found just before the decimal point in non-integral numbers; just to its left in left-to-right systems. In fractions between -1 and +1, it may be written as 0 for the sake of clarity or omitted for the sake of brevity, except if it is the integer, 0.
Among all positional notation systems, the units place is always in multiples of the base raised to the zeroth power, one. This is the only place that is consistent between different bases. The place before it contains multiples of the base (the tens place in decimal). The place following it, just after the decimal, contains multiples of the reciprocal of the base (the tenths place in decimal).
Only one character may be inserted in the units place and that character will be the face value of the units place and it may be any character from zero to one less than the base (0–9 in decimal but 0–F in the Hexadecimal system common in computing). Should the number be a multiple of the base, the units place will be 0. Despite 0 having a face value of nothing, it is important in these system as a placeholder. Neglecting to write a placeholder changes the value of the number.
Read more about this topic: Units Place