Decimal point in the context of Decimal

An abacus (pl. abaci or abacuses), also called a counting frame, is a hand-operated calculating tool which was used from ancient times, in the ancient Near East, Europe, China, and Russia, until largely replaced by handheld electronic calculators, during the 1980s, with some ongoing attempts to revive their use. An abacus consists of a two-dimensional array of slidable beads (or similar objects). In their earliest designs, the beads could be loose on a flat surface or sliding in grooves. Later the beads were made to slide on rods and built into a frame, allowing faster manipulation.

Each rod typically represents one digit of a multi-digit number laid out using a positional numeral system such as base ten (though some cultures used different numerical bases). Roman and East Asian abacuses use a system resembling bi-quinary coded decimal, with a top deck (containing one or two beads) representing fives and a bottom deck (containing four or five beads) representing ones. Natural numbers are normally used, but some allow simple fractional components (e.g. 1⁄2, 1⁄4, and 1⁄12 in Roman abacus), and a decimal point can be imagined for fixed-point arithmetic.

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.

It can be shown that a number is rational if and only if its decimal representation is repeating or terminating. For example, the decimal representation of ⁠1/3⁠ becomes periodic just after the decimal point, repeating the single digit "3" forever, i.e. 0.333.... A more complicated example is ⁠3227/555⁠, whose decimal becomes periodic at the second digit following the decimal point and then repeats the sequence "144" forever, i.e. 5.8144144144.... Another example of this is ⁠593/53⁠, which becomes periodic after the decimal point, repeating the 13-digit pattern "1886792452830" forever, i.e. 11.18867924528301886792452830....

In mathematics and computer science, truncation is limiting the number of digits right of the decimal point.

John Napier of Merchiston (/ˈneɪpiər/ NAY-pee-ər; Latinized as Ioannes Neper; 1 February 1550 – 4 April 1617), nicknamed Marvellous Merchiston, was a Scottish landowner known as a mathematician, physicist, and astronomer. He was the 8th Laird of Merchiston. Napier is best known as the discoverer of logarithms. He also invented the "Napier's bones" calculating device and popularised the use of the decimal point in arithmetic.

Napier's birthplace, Merchiston Tower in Edinburgh, is now part of the facilities of Edinburgh Napier University. There is a memorial to him at St Cuthbert's Parish Church at the west end of Princes Street Gardens in Edinburgh.

A numeric keypad, number pad, numpad, or ten key, is the calculator-style group of ten numeric keys accompanied by other keys, usually on the far right side of computer keyboard. This grouping allows quick number entry with the right hand, without the need to use both hands on number row of main keyboard. On a standard IBM PC keyboard, numpad has 17 keys, including digits 0 to 9, + (addition), - (subtraction), * (multiplication), and / (division) symbols, . (decimal point), Num Lock, and ⌅ Enter keys. On smaller keyboards (such as those found on laptops), the numeric keypad can be implemented as alternative markings on alphabetic keys (usually I-O-P, K-L-;, ,-.-/) or added as a separate unit, that can be connected to a device by means such as USB; some of these may include keys not found on a standard numpad, such as a spacebar or a 00 (or 000) key.

Sometimes it is necessary to distinguish between a key on the numpad and an equivalent key elsewhere on the keyboard. For example, depending on the software in use, pressing the numpad's 0 key may produce different results than pressing the alphanumeric 0 key. In such cases, the numpad-specific key may be indicated as e.g. Numpad 0, NumPad0, Num 0, or likewise to remove ambiguity.