0000

0000 is a four-digit string composed of zeros. As a number, it represents zero; adding leading zeros does not change its value. Leading zeros are commonly used in data formats to enforce fixed width or lexicographic sorting, such as in identifiers, timestamps, or numerical codes.

In computing, 0000 often appears as a placeholder, default, or sentinel value indicating 'no data' or 'zero'. It may also be encountered in source code as a numeric literal; in languages with octal literals a leading zero can indicate octal, but 0000 equals zero in any base.

In calendars, there is no year 0000 in the common AD/CE system. Some astronomical and ISO conventions use a proleptic year numbering that includes a year zero to align with arithmetic, in which 0000 corresponds to 1 BCE.

In other contexts, 0000 may appear as part of fixed-width identifiers, product codes, or serial numbers across databases and software interfaces. Notable associations with 0000 are limited; it is primarily a formatting or numeric representation rather than a concept with its own domain. In related contexts, it is commonly discussed alongside 0, leading zeros, year zero, and octal notation.