Packed Decimal

About

The numeric digits are packed (2 digits per byte) with the last half of the last byte 'F' (for unFormatted).

Signed fields have a 'C' (for Credit / +) or 'D' (for Debit / -) as the last half of the last byte.

To calculate the size of the packed decimal field required to store an x digit number use: (x + 1) / 2

To calculate the number of digits a packed decimal field of size x will store use: (x * 2) - 1

Limits:

COBOL programs can only handle a maximum of 18 digits by default, although this can be extended to 31 via the 'ARITH(EXTEND)' compiler option.

Other:

Also known as 'PD'.

Implied decimal places.

Use:

Mainly used on OS/390, although they can be used elsewhere.

Fastest data type for calculations on OS/390.

Examples

Unsigned

     12345     is encoded in hex as    135
                                       24F

     12345.67  is encoded in hex as    1357
                                       246F
      

Signed

     +12345    is encoded in hex as    135
                                       24C

     -12345.67 is encoded in hex as    1357
                                       246D
      

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Packed Decimal field sizes

No. of digits	No. of bytes		No. of digits	No. of bytes
1	1		17	9
2	2		18	10
3	2		19	10
4	3		20	11
5	3		21	11
6	4		22	12
7	4		23	12
8	5		24	13
9	5		25	13
10	6		26	14
11	6		27	14
12	7		28	15
13	7		29	15
14	8		30	16
15	8		31	16
16	9

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