The EXTERNAL clause specifies that a file connector is external.
EXTERNAL Clause - Format >>-+----+--EXTERNAL-------------------------------------------->< '-IS-'
In a run unit, there is only one representation of an external file; an external file can be referenced by any COBOL program in the run unit that describes the file.
In the File Section, the EXTERNAL clause can be specified only in file description entries. The records appearing in the file description entry need not have the same name in corresponding external file description entries. In addition, the number of such records need not be the same in corresponding file description entries. However, the maximum record length for corresponding external file description entries must be the same.
For EXTERNAL files, the value of all BLOCK CONTAINS clauses of corresponding EXTERNAL files must match within the run unit. This conformance is in terms of character positions only - not upon whether the value was specified as CHARACTERS or as RECORDS.
Use of the EXTERNAL clause does not imply that the associated file-name is a global name.
The TYPEDEF clause cannot be specified in the same data description entry as the EXTERNAL clause, however, the TYPE clause can.