COBOL Decimal Numbers

There are two type of formats for decimal numbers:

1. Zoned Decimal

2. Packed Decimal

1. Zoned Decimal Numbers

-- each byte present 1 numeric value.

-- the sign mark is placed at last byte ( F means an unsigned, C means a positive, D means a negative)

-- for example

    123 => 0x F1 F2 F3 ("123")

    +1234 => 0x F1 F2 F3 C4 ("123D"), 0xC4 == 'D'

    - 12345 => 0x F1 F2 F3 F4 D5 ("1234N"), 0xD5 == 'N'

With EBCDIC coding, '0' = 0xF0, '1'=0xF1, '2'=0xF2, ..., '9'=0xF9

2. Packed Decimal Numbers (COMP-3)

-- each byte present 2 numeric values (but the last byte)

-- the sign is placed at the most-right 4 bits; so the last byte present a numeric value and the sign mark

-- for example

    123 => 0x 12 3F

    +1234 => 0x 01 23 4C

    - 12345 => 0x 12 34 5D

(Compared with ZD, where the sign mark is placed at first half-byte, PD use second half-byte as sign mark)

EBCDIC please refer to  https://zh.wikipedia.org/wiki/EBCDIC