Reserved — National
What it is
Reserved for national use.
DE 113 on the wire
Bitmap position
DE 113 is bit 49 of the secondary bitmap: byte 7, mask 0x80. A secondary bitmap with only DE 113 present reads 0000000000008000 in hex. The secondary bitmap is only sent when bit 1 of the primary bitmap is set, so any message carrying DE 113 has a primary bitmap whose first hex digit is 8 or higher.
Length
DE 113 is variable length (LLLVAR): a 3-digit prefix gives the length of the value in characters, from 0 to 999. A 12-character value is sent as 012 followed by the value. In ASCII the prefix is the bytes 30 31 32; dialects that pack lengths as BCD send 00 12 instead.
Size in the message
At most 1002 bytes when the message travels as text (ASCII or EBCDIC), or 1001 bytes in binary dialects that pack the length prefix as BCD.
Format ans
Format ans means alphanumeric and special: letters, digits, space and punctuation.
What “reserved for national use” means for your parser
DE 113 is left to national bodies: a domestic scheme or network may define it for traffic within one country. ISO fixes only the envelope (LLLVAR, up to 999 characters), so the layout comes from that network's specification. A parser that does not know the national layout should keep the value as an opaque string and pass it on unchanged.
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.