| slovo | definícia |
binary coded decimal
(foldoc) | binary coded decimal
BCD
packed decimal
(BCD, packed decimal) A number representation where a
number is expressed as a sequence of decimal digits and then
each decimal digit is encoded as a four-bit binary number (a
nibble). E.g. decimal 92 would be encoded as the eight-bit
sequence 1001 0010.
In some cases, the right-most nibble contains the sign
(positive or negative).
It is easier to convert decimal numbers to and from BCD than
binary and, though BCD is often converted to binary for
arithmetic processing, it is possible to build hardware that
operates directly on BCD.
[Do calculators use BCD?]
(2001-01-27)
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| | podobné slovo | definícia |
extended binary coded decimal interchange code
(foldoc) | Extended Binary Coded Decimal Interchange Code
EBCDIC
/eb's*-dik/, /eb'see`dik/, /eb'k*-dik/,
/ee`bik'dik`/, /*-bik'dik`/ (EBCDIC) A proprietary 8-bit
character set used on IBM dinosaurs, the AS/400, and
e-Server.
EBCDIC is an extension to 8 bits of BCDIC (Binary Coded
Decimal Interchange Code), an earlier 6-bit character set used
on IBM computers. EBCDIC was [first?] used on the successful
System/360, anounced on 1964-04-07, and survived for many
years despite the almost universal adoption of ASCII
elsewhere. Was this concern for backward compatibility or,
as many believe, a marketing strategy to lock in IBM
customers?
IBM created 57 national EBCDIC character sets and an
International Reference Version (IRV) based on ISO 646 (and
hence ASCII compatible). Documentation on these was not
easily accessible making international exchange of data even
between IBM mainframes a tricky task.
US EBCDIC uses more or less the same characters as ASCII,
but different code points. It has non-contiguous letter
sequences, some ASCII characters do not exist in EBCDIC
(e.g. square brackets), and EBCDIC has some (cent sign,
not sign) not in ASCII. As a consequence, the translation
between ASCII and EBCDIC was never officially completely
defined. Users defined one translation which resulted in a
so-called de-facto EBCDIC containing all the characters of
ASCII, that all ASCII-related programs use.
Some printers, telex machines, and even electronic cash
registers can speak EBCDIC, but only so they can converse with
IBM mainframes.
For an in-depth discussion of character code sets, and full
translation tables, see {Guidelines on 8-bit character codes
(ftp://ftp.ulg.ac.be/pub/docs/iso8859/iso8859.networking)}.
{A history of character codes
(http://tronweb.super-nova.co.jp/characcodehist.html)}.
(2002-03-03)
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