SAB:

您好, 回復問題如下:

1.EAN商品碼是鍵於024字段，指標選用3#。
 ENA是歐洲商品條碼（European Article Number, EAN）後發展為國際商品條碼 （International Article Number），可著錄於024 3_ $a。以下範例，即抄錄自LC MARC 21範例：024 3# $a9780449906200$d51000

2. 上例算一算是13碼。若要著錄此標準號，可請系統公司更改長度。以下是LC的說明，供參考：

EAN Structure and Display Constants

Structure - EAN has 13 digits. For serials, a three-digit prefix (977) is used in combination with the eight-digit International Standard Serial Number (ISSN) or with a nationally administered title number such as the BIPAD number in North America. A two- or five-digit add-on symbology to designate issues may be present.

For paperback books, a three-digit prefix (978) is followed by the first nine characters of the International Standard Book Number (ISBN), omitting the final ISBN check character. An all-numeric Modulus-10 check digit is the 13th character of the EAN. A five-digit supplement may be used to code additional data, e.g., price.

Display Constants - EAN is carried in the MARC record without the internal hyphens or spaces. Hyphens, spaces, and introductory words may be system generated as display constants associated with first indicator value 3 and the content of subfields $a, $d, and $z.

EAN有8碼和13碼之分，13位的組成是這樣的：
國家代碼（前3位）+ 生產商代碼（後4位）+貨品代碼（再5位）。再加最後1碼檢查碼，共13碼。在著錄於MARC格式時, 不加連字符號「-」。
024 3_ $a標準主號碼 $d標準副號碼 $z無效碼

一般所見都是標準的13碼，著錄於$a, 至於副號碼的功用是甚麼, 本人不知, 建議可以請教商品條碼製造商。

錢月蓮敬答  20161119