Card Acceptor Terminal Identification
What it is
Identifies the specific terminal (TID) at the merchant location. Key for reconciliation and fraud tracing.
DE 41 on the wire
Bitmap position
DE 41 is bit 41 of the primary bitmap: byte 6, mask 0x80. A primary bitmap with only DE 41 present reads 0000000000800000 in hex.
Length
DE 41 is fixed length: always 8 characters, with no length prefix. A parser reads exactly that many and moves on, so shorter values are left-aligned and padded with trailing spaces.
Size in the message
At most 8 bytes when the message travels as text (ASCII or EBCDIC).
Format ans
Format ans means alphanumeric and special: letters, digits, space and punctuation.
Specification reference
Defined in ISO 8583:1987 (base). Card networks publish their own dialect tables (Visa BASE I / V.I.P., Mastercard CIS) that refine formats, lengths, and — for private-use elements — the entire layout. Always confirm against the interface specification you implement.