ISO 8583 · Data fields

Field 71Message Number

pyiso8583 starter profilesIndependent explanation

What this field describes

This field carries a message number in the selected profiles.

Read the numbering and reset rules for the relevant exchange. A message number is distinct from the system trace audit number.

Compare the two profiles

Container settings from the pinned pyiso8583 source.
Setting	`default`	`default_ascii`
Value encoding	ASCII	ASCII
Length limit	Exactly 4 bytes	Exactly 4 bytes
Prefix	None	None

Length limits describe encoded values. They exclude any length prefix. The profiles can be customized; these settings do not establish the required fields or accepted values for a live connection.

Read the field boundary

Field 714 bytesASCII value

Read exactly 4 value bytes. The next field begins immediately afterwards under this profile; no length prefix belongs to this field.

Find it in the bitmap

Bitmap: Secondary
Position: 7
Byte: 1
Bit in byte: 7

Positions start at one. Bits are counted from the most significant bit of each bitmap byte. This calculation locates the field’s presence indicator, not its value.