In packed decimal format,
each byte represents two decimal digits. An IBM packed decimal number
consists of a sign and up to 31 digits, thus giving a range of 10
31 −1
to -10
31 + 1. The sign is written in the
rightmost nibble. (A nibble is four bits or half a byte.) A hexadecimal
C indicates a plus sign, and a hexadecimal D indicates a minus sign.
The rest of the nibbles to the left of the sign nibble represent
decimal digits. The hexadecimal values of these digit nibbles correspond
to decimal values. Therefore, only values between '0'x and '9'x can
be used in the digit positions.
If an overflow occurs,
the value that is written is the largest value that fits into the
output field; the value will be positive, negative, or unsigned, as
appropriate.
The following table
contains examples that illustrate packed decimal format:
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a d value
of 2 causes the number to be multiplied by 10 2 |
Note: In these examples, the Value
column represents the value of the data, and the Results column shows
a hexadecimal representation of the bit pattern written by the corresponding
format. (You cannot view this data in a text editor, unless you can
view it in hexadecimal representation.)
The PD
w.d format
writes missing numerical data as -0. When the PD
w.d informat
reads -0, the informat stores -0 as 0.