pulse code modulation: see modulation.

code, in communications, set of symbols and rules for their manipulation by which the symbols can be made to carry information. By this extended definition all written and spoken languages are codes. While these are sufficient and actually quite efficient in transmission of information, they are at times ambiguous and are highly inefficient for telecommunications. For example, a circuit capable of carrying a voice message, e.g., a telephone circuit, could carry several times as much information if that information were represented as telegraphic code. Special codes are also used for representing data inside a computer. Generally speaking, information theory shows that for any particular application there is an optimum code; it does not, unfortunately, tell how to devise the code. Morse code, consisting of a series of dots and dashes, or marks and spaces, is commonly used in telegraphy. In a computer, information is digitally encoded as strings of binary digits or bits. ASCII, the American Standard Code for Information Interchange, is one popular way to represent alphanumeric characters in a binary form. Special error-detecting codes are used extensively in digital systems to ensure the successful transfer of data. One popular method uses an extra bit, called a parity-check bit; if each bit is considered as a 1 or 0 (depending on whether or not it is set), the sum of a fixed number of bits can be made even (or odd) by properly setting the parity bit to a one or zero. Errors are detected on the receiving end simply by checking whether each received word is even (or odd). Audio data on a compact disc is digitally encoded and a special error correcting code is used to detect and correct errors that may have been introduced through manufacturing error or are created during the reading or playing process. Certain arbitrary codes are used to ensure secrecy of communication; merely the message, without the rules by which the symbols are associated, will not provide an eavesdropper with an understandable version of it. See cryptography; signaling.

code, in law, in its widest sense any body of legal rules expressed in fixed and authoritative written form. A statute thus may be termed a code. Codes contrast with customary law (including common law), which is susceptible of various nonbinding formulations, as in the legal opinions of judges. The earliest codes (e.g., the Roman Twelve Tables) met the popular demand that oral regulations be written down so that legal chicanery might be prevented. In later Roman law, however, the term code acquired its modern meaning of a precisely formulated statement of the principles underlying some branch of law (e.g., contracts) or an entire legal system. One of the greatest codes was the Roman Corpus Juris Civilis. In Europe, in the late 18th cent., after the general adoption of civil law by the continental countries, jurists asserted that similar codes were needed, and the parent modern European codification, the Code Napoléon, appeared (1804) and was followed by many others. The civil law code is an attempt to determine in advance what legal exigencies will arise and to furnish the means for meeting them. Basic legal principles (e.g., that contracts express the will of the parties) are worked out in systematic detail and great attention is given to consistency. The movement for codification, however, has been largely unsuccessful in countries where common law prevails, such as the United States, despite the argument that the principles of common law are sometimes uncertain and often contradict one another. Advocates of the common law assert that civil law makes possibly futile attempts to predict and control the course of developments. In the United States the term code is sometimes also applied to the statutes of a state or of the federal government that have been edited to eliminate duplication and inconsistencies and arranged under appropriate headings.

bar code, computer coding system that uses a printed pattern of lines or bars to identify products, mail and packages, customer accounts, and the like. Bar codes are read by optically scanning the printed pattern and using a computer program to decode the pattern. In a linear bar code system, the code itself contains no information about the item to which it is assigned but represents a string of identifying numbers or letters. When the code is read by an optical scanner linked to a computer, the computer can provide and record information about the item, such as its price or the quantity sold, from and to databases.

The original North American Universal Product Code (UPC), which dates to 1971, used a set of two dark (usually black) and two light (usually white) bars of specified thicknesses to represent 12 numbers, but beginning in 2005 the Uniform Code Council, now known as GS1 US, adopted the similar European Article Numbering Code (EAN), which encodes 13 numbers and had become the international standard. The standards for the international product bar code system are managed by GS1, formerly known as EAN International, which is based in Brussels. The dark bars may be from one to three units wide and the light bars from one to four units. For registration purposes two one-unit dark bars are placed at each end and in the middle. Each item is assigned a unique numeric code, which is printed as a bar code on the item's packaging.

So-called two-dimensional (2D) bar codes permit the encoding of information about an item in addition to an identifying code. In a 2D bar code, two axes, or directions, are used for recording and reading the codes and the bar size is reduced, increasing the space available for data in the way that a column of words improves on a column of letters. Some 2D codes do not use bars at all, such as the United Parcel Service's hexagon-based Maxicode.

An emerging technology, radio-frequency identification (RFID), could supplant the bar code in most applications. The newer radio-based devices overcome many of the limitations inherent in the bar code's optical technology.

Universal Product Code: see bar code.

Theodosian Code, Latin Codex Theodosianus, Roman legal code, issued in 438 by Theodosius II, emperor of the East. It was at once adopted by Valentinian III, emperor of the West. The code was intended to reduce and systematize the complex mass of law that had been issued since the reign of Constantine I. To a large extent it was based upon two private compilations, the Gregorian (Codex Gregorianus) and the Hermogenian (Codex Hermogenianus). The Theodosian Code was used in shaping the Corpus Juris Civilis.

Morse code [for S. F. B. Morse], the arbitrary set of signals used on the telegraph (see code). It may also be used with a flash lamp for visible signaling. The international (or continental) Morse code is a simplified form generally used in radio telegraphy. The American Morse differs from the international Morse in 11 letters, in all the numerals except the numeral 4, and in the punctuation code. The unit of the code is the dot, representing a very brief depression of the telegraph key. The dash represents a depression lasting three times as long as a dot. Between the depressions there is a pause equal in time to one dot, except in a few letters and signs, when there is a wait of two dots. The pause between letters in a word lasts as long as one dash, between words it lasts as long as two dashes. The International Morse code is shown in the table entitled Morse Code. Morse code is now mainly used by amateur (ham) radio operators. The U.S. Coast Guard stopped monitoring Morse code transmissions in 1995 when their use in sending distress calls had been almost entirely superseded by automated systems using satellite relay.

International Morse Code

Letters
A	· -
B	- · · ·
C	- · - ·
D	- · ·
E	·
F	· · - ·
G	- - ·
H	· · · ·
I	· ·
J	· - - -
K	- · -
L	· - · ·
M	- -
N	- ·
O	- - -
P	· - - ·
Q	- - · -
R	· - ·
S	· · ·
T	-
U	· · -
V	· · · -
W	· - -
X	- · · -
Y	- · - -
Z	- - · ·

Numbers and Punctuation
1	· - - - -
2	· · - - -
3	· · · - -
4	· · · · -
5	· · · · ·
6	- · · · ·
7	- - · · ·
8	- - - · ·
9	- - - - ·
0	- - - - -
Period	· - · - · -
Comma	- - · · - -

American Morse Code
The American Morse differs in the following symbols:

Letters
C	· ·  ·
F	· - ·
J	- · - ·
L	——
O	·  ·
P	· · · · ·
Q	· · - ·
R	·  · ·
X	· - · ·
Y	· ·  · ·
Z	· · ·  ·

Numbers and Punctuation
1	· - - ·
2	· · - · ·
3	· · · - ·
4	· · · · -
5	- - -
6	· · · · · ·
7	- - · ·
8	- · · · ·
9	- · · -
0	——
Period	· · - - · ·
Comma	· - · -

Code Napoléon or Code Civil, first modern legal code of France, promulgated by Napoleon I in 1804. The work of J. J. Cambacérès and a commission of four appointed by Napoleon I in 1800 was important in making the final draft. The Code Napoléon embodied the private law of France (i.e., law regulating relations between individuals) and, as modified by amendments, it is still in force in that country. It is a revised form of the Roman law, i.e., the civil law, which prevailed generally on the Continent. It shows, of course, many specific French modifications, some based on the Germanic law that had been in effect in N France. The code follows the Institutes of the Roman Corpus Juris Civilis in dividing civil law into personal status (e.g., marriage), property (e.g., easements), and the acquisition of property (e.g., wills), and it may be regarded as the first modern analogue to the Roman work. Not only was it applied by Napoleon to the territories under his control—N Italy, the Low Countries, and some of the German states—but it exerted a strong influence on Spain (and ultimately on the Latin American countries) and on all European countries except England. It was the forerunner, in France and elsewhere, of codifications of the other branches of law, including civil procedure, commercial law, and criminal law. Quebec prov. and the state of Louisiana owe much of their law to the Code Napoléon. In addition to the Code Civil, Napoleon was responsible for four other codes: the Code of Civil Procedure (1807), Commercial Code (1808), Code of Criminal Procedure (1811), and the Penal Code (1811).

Code Civil: see Code Napoléon.

Clarendon Code, 1661-65, group of English statutes passed after the Restoration of Charles II to strengthen the position of the Church of England. The Corporation Act (1661) required all officers of incorporated municipalities to take communion according to the rites of the Church of England and to abjure the Presbyterian covenant. The Act of Uniformity (1662) required all ministers in England and Wales to use and subscribe to the Book of Common Prayer; nearly 2,000 ministers resigned rather than submit to this act. The Conventicle Act (1664) forbade the assembling of five or more persons for religious worship other than Anglican. The Five-Mile Act (1665) forbade any nonconforming preacher or teacher to come within 5 mi (8.1 km) of a city or corporate town where he had served as minister. These laws, named after Edward Hyde, earl of Clarendon, chief minister of Charles II at the time of their passage, decreased the following of numerous dissenting sects, especially the Presbyterians. Clarendon himself opposed their enactment, but after their passage he worked for their enforcement. Charles II, to court popularity with dissenters and to ease the position of Roman Catholics (with whom he was in sympathy), attempted to interfere with the operation of these laws by his unsuccessful declarations of indulgence in 1662 and 1672. As a political device to weaken the Whigs, the Clarendon Code was largely superseded by the Test Act of 1673, although some of the statutes, in modified form, remained in force for some time.

American Standard Code for Information Interchange: see ASCII.

Standard bar code used to identify grocery and other retail merchandise. In the UPC system, the five digits on the left are assigned to a particular manufacturer or maker and the five digits on the right are used by that manufacturer to identify a specific type or make of product.

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Systematic compilation of law or legal principles. The oldest extant fragments of a law code are tablets from the ancient city of Ebla dating to circa 2400 BC. The best-known ancient code is that of Hammurabi. Roman legal records began in the 5th century BC, though the first formal codification, ordered by Justinian I, was not undertaken until the 6th century AD. In the Middle Ages and into the modern era, only local or provincial compilations were attempted. The first major national code was the Napoleonic Code, followed by the German, Swiss, and Japanese codes. In common-law countries such as England and the U.S., law codes have traditionally been less important than the record of judicial decisions, though major codifications were completed in the U.S. in the 20th century (e.g., the U.S. Code, the Uniform Commercial Code). Seealso civil law; German Civil Code.

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Sequence of nucleotides in DNA and RNA that determines the amino acid sequence of proteins. A messenger RNA molecule synthesized from the DNA directs the synthesis of the protein. Three adjacent nucleotides constitute a unit known as a codon; each codon codes for a single amino acid. There are 64 possible codons, 61 of which specify the 20 amino acids that make up proteins. Because most of the 20 amino acids are coded for by more than one codon, the code is called degenerate. Once thought to be identical in all forms of life, the genetic code has been found to vary slightly in certain organisms and in the mitochondria of some eukaryotes.

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System of symbols and rules used for expressing information according to an unvarying rule for replacing a piece of information from one system, such as a letter, word, or phrase, with an arbitrarily selected equivalent in another system. Substitution ciphers are similar to codes except that the rule for replacing the information is known only to the transmitter and the intended recipient of the information. Binary code and other machine languages used in digital computers are examples of codes. Elaborate commercial codes were developed during the early 20th century (see Jean M.E. Baudot, Samuel F. B. Morse). In recent years more advanced codes have been developed to accommodate computer data and satellite communications. Seealso ASCII, cryptography.

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Laws, enacted in the former Confederate states after the American Civil War, that restricted the freedom of former slaves and were designed to assure white supremacy. They originated in the slave codes, which defined slaves as property. In some states these codes included vagrancy laws that targeted unemployed blacks, apprentice laws that made black orphans and dependents available for hire to whites, and commercial laws that excluded blacks from certain trades and businesses and restricted their ownership of property. Northern reaction to the laws helped produce Radical Reconstruction and passage of the 14th and 15th amendments to the Constitution, as well as creation of the Freedmen's Bureau. Many provisions of the black codes were reenacted in the Jim Crow laws and remained in force until the 1964 Civil Rights Act.

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Printed series of parallel bars of varying width used for entering data into a computer system, typically for identifying the object on which the code appears. The width and spacing of the bars represent binary information that can be read by an optical (laser) scanner that is part of a computer system. The coding is used in many different areas of manufacturing and marketing, including inventory control and tracking systems. The bar codes printed on supermarket and other retail merchandise are those of the Universal Product Code (UPC).

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French Code Civil

French civil code enacted by Napoleon in 1804. It clarified and made uniform the private law of France and followed Roman law in being divided into three books: the law of persons, things, and modes of acquiring ownership of things. In Louisiana, the only civil-law state in the U.S., the civil code of 1825 (revised in 1870 and still in force) is closely connected to the Napoleonic Code. Seealso law code.

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Collections of laws and legal interpretations developed under the sponsorship of the Byzantine emperor Justinian I from 529 to 565. Strictly speaking, they did not constitute a new legal code. Rather, Justinian's committees of jurists provided basically two reference works that contained collections of past laws and extracts of the opinions of the great Roman jurists. Also included were an elementary outline of the law and a collection of Justinian's new laws.

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Collections of laws and legal interpretations developed under the sponsorship of the Byzantine emperor Justinian I from 529 to 565. Strictly speaking, they did not constitute a new legal code. Rather, Justinian's committees of jurists provided basically two reference works that contained collections of past laws and extracts of the opinions of the great Roman jurists. Also included were an elementary outline of the law and a collection of Justinian's new laws.

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(1661–65) Four acts, passed in England during the ministry of the earl of Clarendon, designed to cripple the power of the Nonconformists, or Dissenters. The first, the Corporation Act, forbade municipal office to those not taking the sacraments at a parish church; the Act of Conformity excluded them from church offices; the Conventicle Act made meetings for Nonconformist worship illegal; and the Five-Mile Act forbade Nonconformist ministers to live or visit within five miles of any place where they had ministered.

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in full American Standard Code for Information Interchange.

Data-transmission code used to represent both text (letters, numbers, punctuation marks) and noninput device commands (control characters) for electronic exchange and storage. Standard ASCII uses a string of 7 bits (binary digits) for each symbol and can thus represent 2⁷ = 128 characters. Extended ASCII uses an 8-bit encoding system and can thus represent 2⁸ = 256 characters. While ASCII is still found in legacy data, Unicode, with 8-, 16-, and 32-bit versions, has become standard for modern operating systems and browsers. In particular, the 32-bit version now supports all of the characters in every major language.

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