BCD (character encoding)

BCD ("Binary-Coded Decimal"), also called alphanumeric BCD, alphameric BCD, BCD Interchange Code, or BCDIC, is a family of representations of numerals, uppercase Latin letters, and some special and control characters as six-bit character codes.

Unlike later encodings such as ASCII, BCD codes were not standardized. Different computer manufacturers, and even different product lines from the same manufacturer, often had their own variants, and sometimes included unique characters. Other six-bit encodings with completely different mappings, such as Fieldata and Transcode, are sometimes incorrectly termed BCD.

Many variants of BCD encode the characters '0' through '9' as the corresponding binary values.

History

Technically, binary-coded decimal describes the encoding of decimal numbers where each decimal digit is represented by a fixed number of bits, usually four.

With the introduction of the IBM card in 1928, IBM created a code capable of representing alphanumeric information, later adopted by other manufacturers. This code represented the numbers 0-9 by a single punch, and used multiple punches for upper-case letters and special characters. A letter had two punches (zone [12,11,0] + digit [1–9]); most special characters had two or three punches (zone [12,11,0,or none] + digit [2–7] + 8).

BCD

BCD may refer to:

Computing

Organisations

Places

Other uses

Binary-coded decimal

In computing and electronic systems, binary-coded decimal (BCD) is a class of binary encodings of decimal numbers where each decimal digit is represented by a fixed number of bits, usually four or eight. Special bit patterns are sometimes used for a sign or for other indications (e.g., error or overflow).

In byte-oriented systems (i.e. most modern computers), the term unpacked BCD usually implies a full byte for each digit (often including a sign), whereas packed BCD typically encodes two decimal digits within a single byte by taking advantage of the fact that four bits are enough to represent the range 0 to 9. The precise 4-bit encoding may vary however, for technical reasons, see Excess-3 for instance. The ten states representing a BCD decimal digit are sometimes called tetrades (for the nibble typically needed to hold them also known as tetrade) with those don't care-states unused named pseudo-tetrad(e)s or pseudo-decimal digit).

BCD's main virtue is its more accurate representation and rounding of decimal quantities as well as an ease of conversion into human-readable representations, in comparison to binary positional systems. BCD's principal drawbacks are a small increase in the complexity of the circuits needed to implement basic arithmetics and a slightly less dense storage.

SMN1

Survival motor neuron protein also known as component of gems 1 or gemin-1 is a protein that in humans is encoded by the SMN1 gene. Two transcript variants are produced by this gene.

Gene

This gene is part of a 500 kb inverted duplication on chromosome 5q13. This duplicated region contains at least four genes and repetitive elements which make it prone to rearrangements and deletions. The repetitiveness and complexity of the sequence have also caused difficulty in determining the organization of this genomic region. The telomeric and centromeric copies of this gene are nearly identical and encode the same protein.

Clinical significance

Mutations in the telomeric copy of this gene are associated with spinal muscular atrophy; mutations in the centromeric copy do not lead to disease. The centromeric copy may be a modifier of disease caused by mutation in the telomeric copy. The critical sequence difference between the two genes is a single nucleotide in exon 7 which is thought to be an exon splice enhancer. It is thought that gene conversion events may involve the two genes, leading to varying copy numbers of each gene.

Bit (disambiguation)

A bit is a unit of information storage on a computer.

Bit or BIT may also refer to:

Tools and engineering

Arts and entertainment

Organisations

Education

Crook (music)

A crook, also sometimes called a shank, is an exchangeable segment of tubing in a natural horn (or other brass instrument, such as a natural trumpet) which is used to change the length of the pipe, altering the fundamental pitch and harmonic series which the instrument can sound, and thus the key in which it plays.

Master crook and coupler system

Early horns had unalterable lengths and permanently attached mouthpieces. This presented problems in concert situations. A different horn was required for different keys, and the instrument could not be tuned. Around 1700 the Leichnamschneider brothers in Vienna developed a horn with a removable mouthpiece which could be connected to a short piece of tubing, called a master crook. Additional pieces, couplers, of different length were inserted between the master crook and the body of the horn to change the horn's length, and thus the pitch. Fine tuning was done with even shorter segments called tuning bits. This simple and relatively inexpensive solution remained in use even into the 19th century. Charles Tully's Tutor for the French Horn, published in London, recommended this system for beginners as late as 1840.

Bit (money)

The word bit is a colloquial expression referring to specific coins in various coinages throughout the world.

United States

In the United States, the bit is equal to one eighth of a dollar or 12 ¹⁄₂ cents. In the U.S., the "bit" as a designation for money dates from the colonial period, when the most common unit of currency used was the Spanish dollar, also known as "piece of eight", which was worth 8 Spanish silver reales. One eighth of a dollar or one silver real was one "bit".

With the adoption of the decimal U.S. currency in 1794, there was no longer a U.S. coin worth ¹⁄₈ of a dollar but "two bits" remained in the language with the meaning of one quarter dollar, "four bits" half dollar, etc. Because there was no one-bit coin, a dime (10¢) was sometimes called a short bit and 15¢ a long bit. (The picayune, which was originally ¹⁄₂ real or ¹⁄₂ bit (6 ¹⁄₄¢), was similarly transferred to the US 5¢-piece.)

In addition, Spanish coinage, like other foreign coins, continued to be widely used and allowed as legal tender by Chapter XXII of the Act of April 10, 1806 until the Coinage Act of 1857 discontinued the practice.