When a data structure is to be used repeatedly, a table is defined using the OCCURS clause. A subscript is used to reference the individual table elements.
When using subscripting, be careful about setting and referencing elements outside the range defined with the OCCURS clause. Referencing an item using a subscript that is not within the bounds of the table can destroy an area of memory, or cause execution to terminate abnormally.
000010 @OPTIONS MAIN 000020*---------------------------------------------------------------------- 000030* Data declared in an array can be referenced using a subscript. 000040*---------------------------------------------------------------------- 000050 IDENTIFICATION DIVISION. 000060 PROGRAM-ID. SAMPLE. 000070 DATA DIVISION. 000080 WORKING-STORAGE SECTION. 000090 01 ALP PIC X(26) VALUE "ABCDEFGHIJKLMNOPQRSTUVWXYZ". 000100 01 REDEFINES ALP. 000110 02 CHAR OCCURS 26 TIMES PIC X. 000120 01 IN-DATA PIC X. 000130 01 COUNTER PIC 9(2). 000140 PROCEDURE DIVISION. 000150 DISPLAY "Please input one upper-case letter. >>" WITH NO 000155 ADVANCING. 000160 ACCEPT IN-DATA. 000170 PERFORM TEST BEFORE 000180 VARYING COUNTER FROM 1 BY 1 UNTIL COUNTER > 26 000190*---------------------------------------------------------------------- 000200* COUNTER is used as a subscript for CHAR to allow comparison with the 000210* input character. 000220*---------------------------------------------------------------------- 000230 IF IN-DATA = CHAR(COUNTER) THEN 000240*---------------------------------------------------------------------- 000250 EXIT PERFORM 000260 END-IF 000270 END-PERFORM. 000280 IF COUNTER <= 26 THEN 000290 DISPLAY IN-DATA " is character " 000295 COUNTER " in alphabetical order." 000300 ELSE 000310 DISPLAY "The input character is incorrect." 000320 END-IF. 000330 END PROGRAM SAMPLE.
Uniqueness of qualification and subscript reference can also be combined.
000010 @OPTIONS MAIN 000020*---------------------------------------------------------------------- 000030* Data declared in an array is uniquely qualified. 000040*---------------------------------------------------------------------- 000050 IDENTIFICATION DIVISION. 000060 PROGRAM-ID. SAMPLE. 000070 DATA DIVISION. 000080 WORKING-STORAGE SECTION. 000090 01 UPPER-CASE. 000100 02 ALP PIC X(26) VALUE "ABCDEFGHIJKLMNOPQRSTUVWXYZ". 000110 02 REDEFINES ALP. 000120 03 CHAR OCCURS 26 TIMES PIC X. 000130 01 LOWER-CASE. 000140 02 ALP PIC X(26) VALUE "abcdefghijklmnopqrstuvwxyz". 000150 02 REDEFINES ALP. 000160 03 CHAR OCCURS 26 TIMES PIC X. 000170 01 IN-DATA PIC X. 000180 01 COUNTER PIC 9(2). 000190 PROCEDURE DIVISION. 000200 DISPLAY "Please input one upper-case letter. >>" WITH NO 000205 ADVANCING. 000210 ACCEPT IN-DATA. 000220 PERFORM TEST BEFORE 000230 VARYING COUNTER FROM 1 BY 1 UNTIL COUNTER > 26 000240*---------------------------------------------------------------------- 000250* COUNTER is a subscript used to compare the input character. 000260* The subscript is specified after the qualification. 000280*---------------------------------------------------------------------- 000290 IF IN-DATA = CHAR OF UPPER-CASE (COUNTER) THEN 000300*---------------------------------------------------------------------- 000310 EXIT PERFORM 000320 END-IF 000330 END-PERFORM. 000340 IF COUNTER <= 26 THEN 000350 DISPLAY "The lowercase letter corresponding to " IN-DATA " is " 000360 CHAR OF LOWER-CASE (COUNTER)"." 000370 ELSE 000380 DISPLAY "The input character is incorrect." 000390 END-IF. 000400 END PROGRAM SAMPLE.
