The general structure of a record is represented schematically below.

Structure of a MARC 21 Record


CONTROL_FIELD_1     FT     . . .     CONTROL_FIELD_n     FT

DATA_FIELD_1     FT     . . .     DATA_FIELD_n     FT

Each record begins with a leader, which is a fixed field containing information for the processing of the record.  Following the leader is the directory, which is an index to the location of the variable fields (control and data) within the record.  The fields following the directory are all variable fields.  The first variable field is the control number field, which contains an ASCII graphic character string uniquely associated with the record by the organization transmitting the record.  Following the control number field are the rest of the control fields, which contain information useful or required for the processing of the record.  Following the control fields are data fields, which contain general data.  A field terminator (FT), ASCII control character 1E(hex), is used to terminate the directory and each variable field within the record.  A record terminator (RT), ASCII control character 1D(hex), is used as the final character of the record, following the field terminator of the last data field.  These elements of the record are described in more detail in Leader, Directory, and Variable Fields.

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Record Structure