001

001 is a three-character numeric string that, when leading zeros are ignored, represents the number 1. In many contexts it is used as a fixed-width or padded representation of the value 1, ensuring consistent alignment in lists, databases, and identifiers.

Common uses include serial numbers, catalog numbers, part numbers, file or document identifiers, and version labels such as 001, 002, etc. Leading zeros aid sorting by alphanumeric keys and convey a sense of order in a sequence.

In computing, 001 can appear as a literal or as a string. Some programming languages treat numeric literals with a leading zero as octal, so 001 may be octal 1 (decimal 1). In practice, 001 is often treated as decimal 1 or simply as a string that preserves the leading zeros, depending on context. Zero-padding is a standard formatting technique for alignment and readability.

Related concepts include leading zeros and zero-padding.