1.4.2 "COBOL Language Reference" IBM Library Server

1.4.2 External and Internal Resources

Accessible data items usually require that certain representations of data be stored. File connectors usually require that certain information concerning files be stored. The storage associated with a data item or a
X file connector can be external or internal to the program or method in which the resource is declared.

A data item or file connector is external if the storage associated with that resource is associated with the run unit rather than with any
X particular program or method within the run unit. An external resource
X can be referenced by any program or method in the run unit that describes the resource. References to an external resource from different programs
X or methods using separate descriptions of the resource are always to the same resource. In a run unit, there is only one representation of an external resource.

A resource is internal if the storage associated with that resource is
X associated only with the program or method that describes the resource.

External and internal resources can have either global or local names.

A data record described in the Working-Storage Section is given the external attribute by the presence of the EXTERNAL clause in its data description entry. Any data item described by a data description entry subordinate to an entry describing an external record also attains the external attribute. If a record or data item does not have the external
X attribute, it is part of the internal data of the program or method in which it is described.

X Two programs or methods in a run unit can reference the same file connector in the following circumstances:

X An external file connector can be referenced from any program or
X method that describes that file connector.
If a program is contained within another program, both programs can refer to a global file connector by referring to an associated global file-name either in the containing program, or in any program that directly or indirectly contains the containing program.

X Two programs or methods in a run unit can reference common data in the following circumstances:

The data content of an external data record can be referenced from any
X program or method provided that program or method has described that data record.
If a program is contained within another program, both programs can refer to data possessing the global attribute either in the program or in any program that directly or indirectly contains the containing program.

The data records described as subordinate to a file description entry that does not contain the EXTERNAL clause or a sort-merge file description entry, as well as any data items described subordinate to the data description entries for such records, are always internal to the program
X or method describing the file-name. If the EXTERNAL clause is included in the file description entry, the data records and the data items attain the external attribute.

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1.4.2 External and Internal Resources

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