<programming, algorithm> (Or "hashing") A scheme for providing rapid access to data items which are distinguished by some key. Each data item to be stored is associated with a key, e.g. the name of a person. A hash function is applied to the item's key and the resulting hash value is used as an index to select one of a number of "hash buckets" in a hash table. The table contains pointers to the original items. If, when adding a new item, the hash table already has an entry at the indicated location then that entry's key must be compared with the given key to see if it is the same. If two items' keys hash to the same value (a "hash collision") then some alternative location is used (e.g. the next free location cyclically following the indicated one). For best performance, the table size and hash function must be tailored to the number of entries and range of keys to be used. The hash function usually depends on the table size so if the table needs to be enlarged it must usually be completely rebuilt. When you look up a name in the phone book (for example), you typically hash it by extracting its first letter; the hash buckets are the alphabetically ordered letter sections. See also: btree, checksum, CRC, pseudorandom number, random, random number, soundex. (1997-08-03)

Hash Code is a global team programming competition organized by Google. The participants work in teams of 2-4 people solving a programming challenge inspired by software engineering at Google.

hash coding

The coding region of a gene, also known as the coding sequence (CDS), is the portion of a gene's DNA or RNA that codes for protein. Studying the length, composition, regulation, splicing, structures, and functions of coding regions compared to non-coding regions over different species and time periods can provide a significant amount of important information regarding gene organization and evolution of prokaryotes and eukaryotes.

<algorithm> (Or "message digest function") A {one-way function} which takes a variable-length message and produces a fixed-length hash. Given the hash it is computationally infeasible to find a message with that hash; in fact one can't determine any usable information about a message with that hash, not even a single bit. For some one-way hash functions it's also computationally impossible to determine two messages which produce the same hash. A one-way hash function can be private or public, just like an encryption function. MD5, SHA and Snefru are examples of public one-way hash functions. A public one-way hash function can be used to speed up a public-key digital signature system. Rather than sign a long message, which can take a long time, compute the one-way hash of the message, and sign the hash. {sci.crypt FAQ (ftp://src.doc.ic.ac.uk/usenet/usenet-by-group/sci.crypt/)}. (2001-05-10)

In cryptography and computer science, a hash tree or Merkle tree is a tree in which every "leaf" (node) is labelled with the cryptographic hash of a data block, and every node that is not a leaf (called a branch, inner node, or inode) is labelled with the cryptographic hash of the labels of its child nodes. A hash tree allows efficient and secure verification of the contents of a large data structure.

Coding conventions are a set of guidelines for a specific programming language that recommend programming style, practices, and methods for each aspect of a program written in that language. These conventions usually cover file organization, indentation, comments, declarations, statements, white space, naming conventions, programming practices, programming principles, programming rules of thumb, architectural best practices, etc.

<algorithm, cryptography> (SHA) A one-way hash function developped by NIST and defined in standard FIPS 180. SHA-1 is a revision published in 1994; it is also described in ANSI standard X9.30 (part 2). (2003-04-12)

The Secure Hash Algorithms are a family of cryptographic hash functions published by the National Institute of Standards and Technology (NIST) as a U.S.

Levenstein coding, or Levenshtein coding, is a universal code encoding the non-negative integers developed by Vladimir Levenshtein.