# Unpacked decimal number

Unpacked decimal number(: unpacked BCD) is one of the above expressions, defined on the basis of. Zoned decimal number Also called. , It is estimated that it came to be called "unpack" in the sense that it is not a "pack".

One digit of a decimal number is expressed by dividing it into a 4-digit zone and 4-digit numeric bits. A sign bit is assigned to determine whether the last digit of the number is a positive number or a negative number, not a zone bit. The zone bit is 15 for JIS 8 code, 3 for JIS 8 code, 12 for positive number for IBM compatible, 13 for negative number. Since there are differences at the vendor companies regarding the code part, it is very incompatible.

Zone bits

The zone bit is a code indicating that the data is a numerical value. At the same time, it is compatible with the code when representing numbers with letters. Therefore, the code differs depending on the character code that the computer you are using can handle. However, 8-bit character codes are EBCDIC and ASCII (JIS 8), the problem of compatibility is limited. It is rather a sign bit, which is quite problematic and varies among vendors.

Construction

The structure of the unpacked decimal number is shown below, taking as an example the case where + 789 is represented by EBCDIC.

1111 0111 1111 1000 1100 1001
Zone bits Numeric bits Zone bits Numeric bits Sign bits Numeric bits

An example

Expressing +1234 in unpacked decimal number EBCDIC 1111 0001 1111 0010 1111 0011 1100 0100
ASCII (JIS 8) 0011 0001 0011 0010 0011 0011 ???? 0100
EBCDIC expressing -1234 in unpacked decimal number 1111 0001 1111 0010 1111 0011 1101 0100
ASCII (JIS 8) 0011 0001 0011 0010 0011 0011 ???? 0100

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Post Date : 2018-02-12 08:00