HP 3000 Manuals HP 3000 Manuals
Reference to Common Data and Files through External Objects This is a feature of the 1985 ANSI COBOL standard 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 file connector can be external or internal to the program in which the object is declared. A data item or file connector is external if the storage associated with that object is associated with the run unit rather than with any particular program within the run unit. An external object may be referenced by any program in the run unit which describes the object. References to an external object from different programs using separate descriptions of the object are always to the same object. In a run unit, there is only one representative of an external object. An object is internal if the storage associated with that object is associated only with the program that describes the object. 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 attribute, it is part of the internal data of the program in which it is described. A file connector is given the external attribute by the presence of the EXTERNAL clause in the associated file description entry. If the file connector does not have the external attribute, it is internal to the program in which the associated file name is described. The data records described 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 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. A file connector is given a global attribute by the presence of the GLOBAL clause in the file description entry. By specifying the file connector GLOBAL, all the data records associated with the file are automatically given a global attribute and the record description entries do not need to have a GLOBAL clause. However, if a GLOBAL clause is specified in the record description entry and not in the file description entry, only the record name is given a global attribute. For example, the contained programs are not able to reference the file connector (no file I/O is allowed), but are able to reference the record in which a GLOBAL clause was specified. Data records, subordinate data items, and various associated control information described in the linkage of a program are always considered to be internal to the program describing that data. Special considerations apply to data described in the LINKAGE SECTION whereby an association is made between the data records described and other data items accessible to other programs. If a data item possessing the external attribute includes a table accessed with an index, that index does not possess the external attribute. PROGRAM-ID Paragraph Define a subprogram using the PROGRAM-ID paragraph of the IDENTIFICATION DIVISION. Syntax.Description. For more information on the PROGRAM-ID paragraph, see Chapter 5 , "IDENTIFICATION DIVISION." COMMON Clause. The COMMON clause specifies that the program is common, a program contained in another program. A common program is one which, though contained within another program, may be called by any program directly or indirectly contained in that other program. This clause is used in nested and concatenated programs. It facilitates the writing of subprograms which are to be used by all the programs contained within a program. EXTERNAL Clause The EXTERNAL clause is a feature of the 1985 ANSI COBOL standard The EXTERNAL clause specifies that a data item or a file connector is external. The corresponding data items and data group items of an external data record are available to every program in the run unit that describes that record. Syntax. IS EXTERNAL Description. The EXTERNAL clause can only be specified in file description entries or in record description entries in the WORKING-STORAGE SECTION. The data-name specified as the subject of an entry with a level-number of 01 that includes the EXTERNAL clause must not be the same data-name specified for any other data description entry that includes the EXTERNAL clause. The VALUE clause must not be used in any data description entry that includes, or is subordinate to, an entry that includes the EXTERNAL clause. The VALUE clause can be specified for condition-name entries associated with these data description entries. The data contained in the record named by the data-name clause is external. It can be accessed and processed by any program in the run unit that describes and, optionally, redefines it according to the following rules. * Within a run unit, if two or more programs describe the same external data record, each record-name of the record description entries must be the same. The records must define the same number of standard data format characters. However, a program describing an external record can contain a data description entry that includes the REDEFINES clause. The REDEFINES clause then redefines the complete external record. This complete redefinition does not need to occur identically in other programs in the run unit. * The file connector associated with this description entry is an external file connector. Example. The following example illustrates interprogram communication using EXTERNAL items. A main program and a subprogram share an EXTERNAL file and an EXTERNAL data item. IDENTIFICATION DIVISION. PROGRAM-ID. EXTITEMS. ENVIRONMENT DIVISION. INPUT-OUTPUT SECTION. FILE-CONTROL. SELECT SOUT ASSIGN TO "FILEOUTP". DATA DIVISION. FILE SECTION. * * THE EXTERNAL FILE SPECIFICATION * FD SOUT EXTERNAL. 01 REC-OUT. 05 NAME PIC X(20). 05 LOCN PIC X(10). WORKING-STORAGE SECTION. * * THE EXTERNAL DATA-ITEM SPECIFICATION * * NOTE THAT SINCE THE ITEM IS 'EXTERNAL' THE VALUE * CLAUSE MAY NOT BE USED EXCEPT WITHIN A CONDITION-NAME * ASSOCIATED WITH THE DATA ITEM. * 01 EXTERNAL-DATA-ITEM EXTERNAL PIC X(18). 88 X-ITEM VALUE "EXTERNAL-DATA-ITEM". PROCEDURE DIVISION. START-IT. SET X-ITEM TO TRUE. OPEN OUTPUT SOUT. MOVE "JOHN DOE" TO NAME. MOVE "BLDG 48 N" TO LOCN. DISPLAY "DISPLAY OF EXT-DATA-ITEM FROM MAIN ** " EXTERNAL-DATA-ITEM. WRITE REC-OUT. * * CALL SUB1 TO WRITE A RECORD TO THE FILE. NOTE THAT * THE EXTERNAL-DATA-ITEM VARIABLE IS NOT PASSED TO SUB1. * CALL "SUB1". CLOSE SOUT. * * READ/DISPLAY THE SHARED FILE CONTENTS * OPEN INPUT SOUT. READ-FILE-RECS. READ SOUT AT END CLOSE SOUT STOP RUN. DISPLAY REC-OUT. GO TO READ-FILE-RECS. $CONTROL SUBPROGRAM IDENTIFICATION DIVISION. PROGRAM-ID. SUB1. ENVIRONMENT DIVISION. INPUT-OUTPUT SECTION. FILE-CONTROL. SELECT SOUT ASSIGN TO "FILEOUTP". DATA DIVISION. FILE SECTION. FD SOUT EXTERNAL. 01 REC-OUT. 05 NAME PIC X(20). 05 LOCN PIC X(10). WORKING-STORAGE SECTION. 01 EXTERNAL-DATA-ITEM EXTERNAL PIC X(18). PROCEDURE DIVISION. * * NOTE THAT SUB1 DOES NOT REQUIRE A 'USING' CLAUSE TO * ACCESS THE EXTERNAL DATA ITEM OR A FILE 'OPEN' TO * ACCESS THE OUTPUT FILE. * START-IT. MOVE "MARY JANE" TO NAME. MOVE "BLDG 66 W" TO LOCN. DISPLAY "DISPLAY OF EXT-DATA-ITEM FROM SUB1 ** " EXTERNAL-DATA-ITEM. WRITE REC-OUT. GOBACK. When this example is compiled using the ANSI85 entry point, and run, it produces the following output: DISPLAY OF EXT-DATA-ITEM FROM MAIN ** EXTERNAL-DATA-ITEM DISPLAY OF EXT-DATA-ITEM FROM SUB1 ** EXTERNAL-DATA-ITEM JOHN DOE BLDG 48 N MARY JANE BLDG 66 W GLOBAL Clause The GLOBAL clause is a feature of the 1985 ANSI COBOL standard The GLOBAL clause specifies that the data item or file connector can be referenced by the contained programs within a nested program in which the item is declared global. Syntax. IS GLOBAL Description. The following rules should be observed when using GLOBAL clause: * The GLOBAL clause can only be specified in the file description entries in the FILE SECTION or in the 01 record description entries in the FILE SECTION and the WORKING-STORAGE SECTION. * The GLOBAL clause can be specified in the record description entries which have unique names. * If the SAME RECORD AREA clause is specified for several files, the record description entries or the file description entries for these files must not include a GLOBAL clause. * If the GLOBAL clause is used in a record description entry that contains a REDEFINES clause, only the subject of the REDEFINES clause will be given the global attribute. * If the GLOBAL clause is used in a record description entry that contains a table and index name, the index name is automatically given the global attribute. * If the GLOBAL clause is used in a record description entry that contains a condition name defined with a level 88, the condition name is automatically given the global attribute.
![[]](../../pic3k/M011820/FFN1223c50.gif)