Codebook

A codebook contains a lookup table for coding and decoding; each word or phrase has one or more strings which replace it.

The distribution and physical security of codebooks presents a special difficulty in the use of codes compared to the secret information used in ciphers, the key, which is typically much shorter.

In social sciences, a codebook is a document containing a list of the codes used in a set of data to refer to variables and their values, for example locations, occupations, or clinical diagnoses.

Codebooks were also used in 19th- and 20th-century commercial codes for the non-cryptographic purpose of data compression.

The usage is standardized by 3GPP, for example in the document TS 38.331, NR; Radio Resource Control (RRC); Protocol specification.

U.S. State Department code book issued in 1899, an example of a one-part code, at the National Cryptologic Museum
Page 187 of the State Department 1899 code book, a one-part code with a choice of code word or numeric ciphertext. Numeric codes are prefixed by the page number.