isCOBOL Evolve : Language Reference : Data Division : FILE Section : File description
File description
In a COBOL program the file description entry (FD or SD entry) represents the highest level of organization in the File Section. The File Section header is followed by a file description entry consisting of a level indicator (FD/SD), a file-name, and a series of independent clauses. The clauses of a file description entry specify the size of the logical and physical records, the names of the records which comprise the file, and finally the number of lines to be written on a logical printer page.
General format
Level-Indicator File-Name
   [ IS EXTERNAL [ AS External-Name ] ]
 
   [ IS GLOBAL ]
 
   [ CODE-SET  [IS ] Alphabet-1 ]
 
   [ LABEL {RECORD } [IS ] {STANDARD} ] 
           {RECORDS} [ARE] {OMITTED } 
 
   [ BLOCK CONTAINS [Integer-1 TO] Integer-2 {RECORDS   } ]  
                                             {CHARACTERS}  
 
   [ RECORD { CONTAINS Integer-3 CHARACTERS                                                             } ] 
            { IS VARYING IN SIZE [ FROM Integer-4 ] [ TO Integer-5 ] CHARACTERS [ DEPENDING ON Depend ] }
            { CONTAINS Integer-6 TO Integer-7 CHARACTERS                                                }
 
   [ VALUE OF LABEL IS Literal-1 ]
 
   [ VALUE OF {FILE-ID} IS Id-Name ] 
              {ID     }  
 
   [ VALUE OF Literal-1 IS {Literal-2  } ] 
                           {Data-item-1}
 
   [ LINAGE IS Page-Lines LINES
 
     [WITH FOOTING AT Footing-Line ]
 
     [LINES AT TOP Top-Lines ]
 
     [LINES AT BOTTOM Bottom-Lines ] ]
 
   [ DATA {RECORD  IS } {Record-Name} ... ] 
          {RECORDS ARE}
   [ RECORDING MODE IS {V}          ]
                       {F}
                       {U}
                       {S}
                       {VARIABLE}
                       {FIXED}
   [ {REPORT } [IS ] Report-Name ]
     {REPORTS} [ARE]
Syntax rules
1. Level-Indicator must precede File-Name.
2. File-Name is a User-defined word, as defined in the Definitions section in the Preface of this document.
3. File-Name must have a corresponding entry in the FILE-CONTROL Paragraph of the INPUT-OUTPUT Section in the Environment Division.
4. The clauses which follow File-Name may appear in any order.
5. Integer-1, Integer-2, Integer-3, Integer-4, Integer-5, Integer-6 and Integer-7 are Integers, as defined in the Definitions section in the Preface of this document.
6. Depend is a Numeric Data Item, as defined in the Definitions section in the Preface of this document.
7. Id-Name can be either a Data Item or a Nonnumeric Literal, as defined in the Definitions section in the Preface of this document.
8. Page-Lines, Footing-Line, Top-Lines and Bottom-Lines can be either Numeric Data Items or a Integers, as defined in the Definitions section in the Preface of this document.
9. V and VARIABLE are synonymous.
10. F and FIXED are synonymous.
11. Literal-1 and Literal-2 are non-numeric literals.
12. Data-Item-1 is an alphanumeric data item.
13. Alphabet-1 is the name of an alphabet declared in the SPECIAL-NAMES Paragraph.
14. The CODE-SET clause may be associated only with a sequential file.
15. If the CODE-SET clause is used, then only USAGE DISPLAY items may appear in the file's record description entry. In addition, every signed numeric field must have a SIGN IS SEPARATE clause.
General rules
1. Level-Indicator may be FD to identify the beginning of a file description entry or SD to identify the beginning of a sort file description entry.
2. When the IS EXTERNAL clause is specified, the file will be shared among all programs that declare it.
3. The AS phrase of the EXTERNAL clause is treated as a commentary.
4. The IS GLOBAL clause is treated as a commentary.
5. The LABEL clause is treated as a commentary.
6. VALUE OF Literal-1 is treated as a commentary.
7. Integer-1 must be less than or equal to Integer-2. The BLOCK clause is treated as a commentary.
8. The RECORD clause specifies the number of character positions in a fixed length record, or specifies the range of character positions in a variable length record. If the number of character positions does vary, the clause specifies the minimum and maximum number of character positions.
a. If the RECORD clause is not specified, the size of each data record is completely defined in the record description entry. Relative Files cannot have variable record size, so the maximum record size is used.
b. No record description entry for the file may specify a number of character positions greater than Integer-3.
c. When Integer-3 is specified, the record length is fixed. Integer-3 specifies the number of character positions contained in each record in the file.
d. Record descriptions for the file must not describe records which contain a lesser number of character positions than that specified by Integer-4 nor records which contain a greater number of character positions than that specified by Integer-5.
e. Integer-4 must be less than or equal to Integer-5.
f. The VARYING clause is used to specify variable length records. Integer-4 specifies the minimum number of character positions to be contained in any record of the file. Integer-5 specifies the maximum number of character positions in any record of the file.
g. The number of character positions associated with a record description is determined by the sum of the number of character positions in all elementary data items excluding redefinitions and renamings, plus any implicit FILLER due to synchronization. If a table is specified:
i. The minimum number of table elements described in the record is used in the summation above to determine the minimum number of character positions associated with the record description.
ii. The maximum number of table elements described in the record is used in the summation above to determine the maximum number of character positions associated with the record description.
h. If Integer-4 is not specified, the minimum number of character positions to be contained in any record of the file is equal to the least number of character positions described for a record in that file.
i. If Integer-5 is not specified, the maximum number of character positions to be contained in any record of the file is equal to the greatest number of character positions described for a record in that file.
j. If Depend is specified, the number of character positions in the record must be placed into the data item referenced by Depend before any RELEASE, REWRITE, or WRITE Statement is executed for the file.
k. If Depend is specified, the execution of a DELETE, RELEASE, REWRITE, START, or WRITE Statement or the unsuccessful execution of a READ or RETURN Statement does not alter the content of the data item referenced by Depend.
l. During the execution of a RELEASE, REWRITE, or WRITE Statement, the number of character positions in the record is determined by the following conditions:
i. If Depend is specified, by the content of the data item referenced by Depend.
ii. If Depend is not specified and the record does not contain a variable occurrence data item, by the number of character positions in the record.
iii. If Depend is not specified and the record does contain a variable occurrence data item, by the sum of the fixed portion and that portion of the table described by the number of occurrences at the time of execution of the I-O Statement.
m. If Depend is specified, after the successful execution of a READ or RETURN Statement for the file, the contents of the data item referenced by Depend will indicate the number of character positions in the record just read.
n. If the INTO Phrase is specified in the READ or RETURN Statement, the number of character positions in the current record that participate as the sending data items in the implicit MOVE Statement is determined by the following conditions:
i. If Depend is specified, by the content of the data item referenced by Depend.
ii. If Depend is not specified, by the value that would have been moved into the data item referenced by Depend had Depend been specified.
o. When Integer-6 and Integer-7 are specified, they refer to the minimum number of characters in the smallest size data record and the maximum number of characters in the largest size data record, respectively. However, in this case, the size of each data record is completely defined in the record description entry.
p. The size of each data record is specified in terms of the number of character positions required to store the logical record, regardless of the types of characters used to represent the items within the logical record. The size of a record is determined by the sum of the number of characters in all fixed length elementary items plus the sum of the maximum number of characters in any variable length item subordinate to the record. This sum may be different from the actual size of the record.
9. Id-Name is the name of the file to be opened. Its value overrides the value of File specified in the FILE-CONTROL Paragraph of the INPUT-OUTPUT Section in the Environment Division.
10. The LINAGE clause provides a means for specifying the depth of a logical page in terms of number of lines. It also provides for specifying the size of the top and bottom margins on the logical page, and the line number, within the page body, at which the footing area begins.
a. The LINAGE clause can be specified only for Sequential Files.
b. The LINAGE clause provides a means for specifying the size of a logical page in terms of number of lines. The logical page size is the sum of the values referenced by each phrase except the FOOTING Phrase. If the LINES AT TOP or LINES AT BOTTOM Phrases are not specified, the values of these items are zero. If the FOOTING Phrase is not specified, no end-of-page condition independent of the page overflow condition exists.
 
There is not necessarily any relationship between the size of the logical page and the size of a physical page.
c. Page-Lines specifies the number of lines that can be written and/or spaced on the logical page. The value must be greater than zero. That part of the logical page in which these lines can be written and/or spaced is called the page body.
d. Footing-Line specifies the line number within the page body at which the footing area begins. The value must be greater than zero and not greater than Page-Lines.
 
The footing area comprises the area of the page body between the line represented by Footing-Line and the line represented by Page-Lines, inclusive.
e. Top-Lines specifies the number of lines that comprise the top margin on the logical page. This area is not writable. The value may be zero.
f. Bottom-Lines specifies the number of lines that comprise the bottom margin on the logical page. This area is not writable. The value may be zero.
g. Page-Lines, Top-Lines, and Bottom-Lines, if specified, are used at the time the file is opened by the execution of an OPEN Statement with the OUTPUT Phrase, to specify the number of lines that comprise each of the indicated sections of a logical page. Footing-Line, if specified, is used at that time to define the footing area. These values are used for all logical pages written for that file during a given execution of the program.
h. The values of the data items referenced by Page-Lines, Top-Lines, and Bottom-Lines, if specified, are used as follows:
i. The values of the data items at the time an OPEN Statement with the OUTPUT Phrase is executed for the file are used to specify the number of lines that are to comprise each of the indicated sections for the first logical page.
ii. The values of the data items, at the time a WRITE Statement with the ADVANCING PAGE Phrase is executed or a page overflow condition occurs are used to specify the number of lines that are to comprise each of the indicated sections for the next logical page.
i. Footing-Line is used to define the footing area for the first logical page at the time an OPEN Statement with the OUTPUT Phrase is executed for the file. At the time a WRITE Statement with the ADVANCING PAGE Phrase is executed or a page overflow condition occurs, it is used to define the footing area for the next logical page.
j. A LINAGE-COUNTER is generated by the presence of a LINAGE clause. The value in the LINAGE-COUNTER at any given time represents the line number at which the device is positioned within the current page body. The rules governing the LINAGE-COUNTER are as follows:
i. A separate LINAGE-COUNTER is supplied for each file described in the File Section whose file description entry contains a LINAGE clause.
ii. LINAGE-COUNTER may be referenced only in Procedure Division statements; however only the input-output control system may change the value of LINAGE-COUNTER. Since more than one LINAGE-COUNTER may exist in a program, the user must qualify LINAGE-COUNTER by File-Name when necessary.
iii. LINAGE-COUNTER is automatically modified, according to the following rules, during the execution of a WRITE Statement to an associated file:
• When the ADVANCING PAGE Phrase of the WRITE Statement is specified, the LINAGE-COUNTER is automatically reset to one. During the resetting of LINAGE-COUNTER to the value one, the value of LINAGE-COUNTER is implicitly increased incrementally to exceed the value specified by Page-Lines.
• When the ADVANCING Line-Count Phrase of the WRITE Statement is specified, the LINAGE-COUNTER is increased incrementally by Line-Count.
• When the ADVANCING Phrase of the WRITE Statement is not specified, the LINAGE-COUNTER is increased incrementally by the value one.
• The value of LINAGE-COUNTER is automatically reset to one when the device is repositioned to the first line that can be written on for each of the succeeding logical pages.
iv. The value of LINAGE-COUNTER is automatically set to one at the time an OPEN Statement with the OUTPUT Phrase is executed for the associated file.
k. Each logical page is contiguous to the next with no additional spacing provided.
11. The DATA RECORDS clause is treated as a commentary.
12. RECORDING MODE requires the -cv compiler option and is treated as a commentary.
13. Report-Name must be the same as the Report-Name used in the Report Description (RD) entry.
14. The CODE-SET clause associates a character set with a sequential file. If the character set is not the native character set, then a translation to the native set is also implied.