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| Cardinal | 0 zero |
| Ordinal | 0th zeroth |
| Factorization | <math> 0 <math> |
| Divisors | N/A |
| Roman numeral | N/A |
| Binary | 0 |
| Octal | 0 |
| Duodecimal | 0 |
| Hexadecimal | 0 |
Zero (0) is a number that precedes the positive one, and all positive numbers, and follows negative one, and all negative numbers.
Zero is a number introduced by Indian mathematicians, which means nothing, null, void or an absence of value. For example, if the number of your brothers is zero, then you have no brothers. If the difference between the number of pieces in two piles is zero, it means the two piles have the same number of pieces.
In certain calendars it is common usage to omit the year zero when extending the calendar to years prior to its introduction: see proleptic Gregorian calendar and proleptic Julian calendar.
The numeral or digit zero is used in numeral systems, where the position of a digit signifies its value. Successive positions of digits have higher values, so the digit zero is used to skip a position and give appropriate value to the preceding and following digits.
By about 300 BC, the Babylonians had started to use a basic numeral system and were using two slanted wedges to mark an empty space. However, this symbol did not have any true function other than to be a placeholder. In general, zero did not have its own Roman numeral, but the concept of zero as a number was well known by all medieval computists (calculators of Easter). They included zero (via the Latin word nullae meaning nothing) as one of nineteen epacts, or the age of the moon on March 22. The first three epacts were nullae, xi, and xxii (written in miniscule or lower case).
The use of zero as a number unto itself was a relatively late addition to mathematics, thought to be introduced by Indian mathematicians. An early study of the zero by Brahmagupta dates to 628. However, the first known computist to use zero was Dionysius Exiguus in 525, but the concept of zero was no doubt well known earlier. About 725, Bede or one of his colleagues used the letter N, the initial of nullae, in a table of epacts, all written in Roman numerals.
Zero was also used as a numeral in Pre-Columbian Mesoamerica. It was used by the Olmec and subsequent civiliations; see also: Maya numerals.
The word zero comes from Arabic sifr, meaning "empty". The English word cipher comes from sifr.
Zero (0) is both a number and a numeral. The natural number following zero is one and no natural number precedes zero. Zero may or may not be counted as a natural number, depending on the definition of natural numbers.
In set theory, the number zero is the size of the empty set: if you do not have any apples, then you have zero apples. In fact, in certain axiomatic developments of mathematics from set theory, zero is defined to be the empty set.
The following are some basic rules for dealing with the number zero. These rules apply for any complex number x, unless otherwise stated.
Human beings usually count things from one, not zero. Yet in computer science zero has become the popular indication for a starting point. For example, in almost all old programming languages, an array starts from 1 by default, which is natural for humans. As programming languages have developed, it has become more common that an array starts from zero by default. This is because, with a one-based index, one must be subtracted to obtain a correct offset for things like obtaining the location of a specific element.
If your zero is centre-dotted and letter-O is not, or if letter-O looks almost rectangular but zero looks more like an American football stood on end (or the reverse), you're probably looking at a modern character display (though the dotted zero seems to have originated as an option on IBM 3270 controllers). If your zero is slashed but letter-O is not, you're probably looking at an old-style ASCII graphic set descended from the default typewheel on the venerable ASR-33 Teletype (which causes problems for Norwegians and Danish who use Ø as a letter).
If letter-O has a slash across it and the zero does not, your display is tuned for a very old convention used at IBM and a few other early mainframe makers (which is even more problematic for Scandinavians because it means two of their letters collide). Some Burroughs/Unisys equipment displays a zero with a reversed slash. And yet another convention common on early line printers left zero unornamented but added a tail or hook to the letter-O so that it resembled an inverted Q or cursive capital letter-O.
The typeface used on some European number plates for cars distinguish the two symbols by making the O rather egg-shaped and the zero more rectangular, but most of all by opening the zero on the upper right side, so here the circle is not closed any more (as in German plates).
In computing, zero is a default digit, meaning none and initial value. To zero (or zeroise or zeroize) a set of data means to set every bit in the data to zero (or off). This is usually said of small pieces of data, such as bits or words (especially in the construction "zero out").
Zero means to erase, to discard all data from. This is often said of disks and directories, where "zeroing" need not involve actually writing zeroes throughout the area being zeroed. One may speak of something being "logically zeroed" rather than being "physically zeroed".
A Null pointer in C programming language usually contains the memory address of zero. However, it is not required to be zero. Some computer architectures use bit patterns other than zero as their null pointer.
This article was originally based on material from the Free On-line Dictionary of Computing and is used under the GFDL.
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