How to provide data in Data elements of ISO-8583 message ?

Data elements are the individual fields carrying the transaction information. There are up to 128 data elements specified in the original ISO 8583:1987 standard, and up to 192 data elements in later releases.

The 1993 revision added new definitions, deleted some, while leaving the message format itself unchanged.

While each data element has a specified meaning and format, the standard also includes some general purpose data elements and system-or country-specific data elements which vary enormously in use and form from implementation to implementation.

Each data element is described in a standard format which defines the permitted content of the field (numeric, binary, etc.) and the field length (variable or fixed)

a   Alpha, including blanks

n   Numeric values only

s   Special characters only

an   Alphanumeric

as   Alpha & special characters only

ns   Numeric and special characters only

ans   Alphabetic, numeric and special characters.

b   Binary data

z   Tracks 2 and 3 code set as defined in ISO/IEC 7813 and ISO/IEC 4909 respectively

. or .. or ...   Variable field length indicator, each . indicating a digit.

x or xx or xxx   Fixed length of field or maximum length in the case of variable length fields.

Additionally, each field may be either fixed or variable length. If variable, the length of the field will be preceded by a length indicator.

Fixed

no field length used

LLVAR or (..xx)

Where LL < 100, means two leading digits LL specify the field length of field

VARLLLVAR or (...xxx)

Where LLL < 1000, means three leading digits LLL specify the field length of field

VARLL and LLL are hex or ASCII.

A VAR field can be compressed or ASCII depending of the data element type.

LL can be 1 or 2 bytes.

For example, if compressed as one hex byte,'27x means there are 27 VAR bytes to follow.

If ASCII, the two bytes '32x, '37x mean there are 27 bytes to follow.

3 digit field length LLL uses 2 bytes with a leading '0' nibble if compressed, or 3 bytes if ASCII.

The format of a VAR data element depends on the data element type.

If numeric it will be compressed, e.g. 87456 will be represented by 3 hex bytes '087456x.

If ASCII then one byte for each digit or character is used, e.g. '38x, '37x, '34x, '35x, '36x.