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BCD (binary-coded decimal), also called alphanumeric BCD, alphameric BCD, BCD Interchange Code, [1] or BCDIC, [1] 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 ...
BCD alphamerics are encoded using digit pairs, with the "zone" in the even-addressed digit and the "digit" in the odd-addressed digit, the "zone" being related to the 12, 11, and 0 "zone punches" as in the 1400 series. Input/output translation hardware converted between the internal digit pairs and the external standard 6-bit BCD codes.
This is a list of some binary codes that are (or have been) used to represent text as a sequence of binary digits "0" and "1". Fixed-width binary codes use a set number of bits to represent each character in the text, while in variable-width binary codes, the number of bits may vary from character to character.
The Aiken code (also known as 2421 code) [1] [2] is a complementary binary-coded decimal (BCD) code. A group of four bits is assigned to the decimal digits from 0 to 9 according to the following table. The code was developed by Howard Hathaway Aiken and is still used today in digital clocks, pocket calculators and similar devices [citation needed].
A code point is a value or position of a character in a coded character set. [10] A code space is the range of numerical values spanned by a coded character set. [10] [12] A code unit is the minimum bit combination that can represent a character in a character encoding (in computer science terms, it is the word size of the character encoding).
Six-bit BCD code was the adaptation of the punched card code to binary code. IBM applied the terms binary-coded decimal and BCD to the variations of BCD alphamerics used in most early IBM computers, including the IBM 1620 , IBM 1400 series , and non- decimal architecture members of the IBM 700/7000 series .
A numeric character reference in HTML refers to a character by its Universal Character Set/Unicode code point, and uses the format &#nnnn; or &#xhhhh; where nnnn is the code point in decimal form, and hhhh is the code point in hexadecimal form. The x must be lowercase in XML documents.
The x87 coprocessor has BCD support in the form of a pair of load (FBLD) and store-and-pop (FBSTP) instructions. The former loads a 80-bit BCD integer into the FPU, while the latter writes a FPU value as a 80-bit integer value into the memory. Inside of the FPU, the values are stored as normal x87 extended-precision floats. Unlike the integer ...