Reference modification is used to refer to a portion of a character data item.
When using reference modification, be careful about setting and referencing outside the scope, or length of the data field being referenced. Reference modification that exceeds the actual area length can destroy data or cause execution to terminate abnormally by referencing an incorrect area of memory.
000010 @OPTIONS MAIN 000020*------------------------------------------------------------------------- 000030* Reference modification enables part of character string data to be 000035* specified. 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 IN-DATA PIC X. 000110 01 COUNTER PIC 9(2). 000120 PROCEDURE DIVISION. 000130 DISPLAY "Please input one upper-case letter. >>" WITH NO ADVANCING. 000140 ACCEPT IN-DATA. 000150 PERFORM TEST BEFORE 000160 VARYING COUNTER FROM 1 BY 1 UNTIL COUNTER > 26 000170*------------------------------------------------------------------------- 000180* Reference modification can specify character data of 000185* (starting location: Length). 000190*------------------------------------------------------------------------- 000200 IF IN-DATA = ALP(COUNTER:1) THEN 000210*------------------------------------------------------------------------- 000220 EXIT PERFORM 000230 END-IF 000240 END-PERFORM. 000250 IF COUNTER <= 26 THEN 000260 DISPLAY IN-DATA " is character " COUNTER " in alphabetical order." 000270 ELSE 000280 DISPLAY "The input character is incorrect." 000290 END-IF. 000300 END PROGRAM SAMPLE.
Uniqueness of qualification and reference modification may also be combined.
000010 @OPTIONS MAIN 000020*------------------------------------------------------------------------- 000030* A data name that must be uniquely qualified can also be reference 000035* modified. 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 01 LOWER-CASE. 000120 02 ALP PIC X(26) VALUE "abcdefghijklmnopqrstuvwxyz". 000130 01 IN-DATA PIC X. 000140 01 COUNTER PIC 9(2). 000150 PROCEDURE DIVISION. 000160 DISPLAY "Please input one upper-case letter. >>" WITH NO ADVANCING. 000170 ACCEPT IN-DATA. 000180 PERFORM TEST BEFORE 000190 VARYING COUNTER FROM 1 BY 1 UNTIL COUNTER > 26 000200*------------------------------------------------------------------------- 000210* COUNTER is used as a subscript and the input character is compared. 000220* The reference modifier is specified after the qualification to 000230* reference-modify the uniquely qualified data. 000240*------------------------------------------------------------------------- 000250 IF IN-DATA = ALP OF UPPER-CASE (COUNTER:1) THEN 000260*------------------------------------------------------------------------- 000270 EXIT PERFORM 000280 END-IF 000290 END-PERFORM. 000300 IF COUNTER <= 26 THEN 000310 DISPLAY "The lower-case letter corresponding to " IN-DATA " is " 000320 ALP OF LOWER-CASE (COUNTER:1)"." 000330 ELSE 000340 DISPLAY "The input character is incorrect." 000350 END-IF. 000360 END PROGRAM SAMPLE.
