shihab, did you get your question solved?

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Thanks,
The Quomon Admin Team

short answer: right after the message type.
Long answer: depends on the format or flavour of your iso.

It's like this: the ISO-message roughly exists of 3 things:
- message type (MTI)
- bitmap(s)
- data (elements)

The message type can be packed or unpacked and if unpacked, it can be either EBCDIC or ASCII.
If it's packed (like with "Hypercom" iso or Visa ISO). each byte contains 2 numbers, if you look at the hex value, which you have to "nibble" to get the expanded value.
So if your message type (and other numerical data elements) is packed, the message type is your first 2 bytes instead of your first 4 bytes, after which comes your bitmap.

Your bitmap can be either single, double or triple and also can be either hex or binary.
A normal Point of Sale message contains a single binary bitmap, i.e. 8 bytes with 64 bits turned on or off.
After you figure out which bits are on or off, you start parsing the data elements based on the bitmap data element definition, the fact if they're packed or not (if numeric), they are variable length and if they're alpha numeric, if they're ASCII or EBCDIC.

It's complicated but once you make one good routine with your data elements, format all defined in tables, you'll breeze through any type of ISO.

I'm programming on a daily basis with Hypercom ISO, Visa, Mastercard, Discover and another 3rd party vendor and they're all a bit different ...

Regards,

Koos Bezemer
Curacao