* Test4.cbl

IDENTIFICATION DIVISION.
  PROGRAM-ID Test4

DATA DIVISION.
  WORKING-STORAGE SECTION.
    01 My-List               PIC S9(9) OCCURS 100 TIMES.
    01 List-Max              PIC S9(9).
    01 R                     PIC S9(9).

PROCEDURE DIVISION.
  COMPUTE List-Max = 100.
  CALL Init USING BY CONTENT List-Max BY REFERENCE My-List.
  COMPUTE R = 1.
  CALL Cons-My-List USING BY CONTENT R, My-List BY REFERENCE My-List.
  DISPLAY My-List (1).
  STOP RUN.

* Init is a subprogram that initializes a list of 100 elements.
* By convention, the first element of the list indicates the length of the
* list. 

IDENTIFICATION DIVISION.
  PROGRAM-ID Init IS COMMON PROGRAM

DATA DIVISION.
  WORKING-STORAGE SECTION.
* empty

  LINKAGE SECTION.
    01 List-Max              PIC S9(9).
    01 Result                PIC S9(9) OCCURS 100 TIMES.

PROCEDURE DIVISION USING List-Max, Result.
  IF List-Max NOT = 100 
* generate a run-time error if the lists are of incompatible sizes
    COMPUTE Result (101) = 0
  ELSE
    COMPUTE Result (1) = 0
  END-IF.
  EXIT PROGRAM.

END PROGRAM Init.

* Cons is a subprogram that inserts an item onto the front of a list of 
* 100 elements. By convention, the first element of the list indicates the 
* length of the list. There is no error checking whether the list overflows 
* or not - it will cause a run-time error.

IDENTIFICATION DIVISION.
  PROGRAM-ID Cons IS COMMON PROGRAM

DATA DIVISION.
  WORKING-STORAGE SECTION.
    01 I                     PIC S9(9).
    01 List-Length           PIC S9(9).

  LINKAGE SECTION.
    01 Item                  PIC S9(9).
    01 List                  PIC S9(9) OCCURS 100 TIMES.
    01 Result                PIC S9(9) OCCURS 100 TIMES.

PROCEDURE DIVISION USING Item, List, Result.
  COMPUTE List-Length = List (1) + 1.
  COMPUTE List (1) = List-Length.
  COMPUTE List (List-Length) = Item.
  COMPUTE I = List-Length.
  PERFORM UNTIL I = 0
    COMPUTE Result (I) = List (I)
    COMPUTE I = I - 1
  END-PERFORM.
  EXIT PROGRAM.

END PROGRAM Cons.

* Cons-My-List is a subprogram that adds numbers to a list, My-List, from
* R to 10.

IDENTIFICATION DIVISION.
  PROGRAM-ID Cons-My-List IS COMMON PROGRAM

DATA DIVISION.
  WORKING-STORAGE SECTION.
*   empty

  LINKAGE SECTION.
    01 R                     PIC S9(9).
    01 My-List               PIC S9(9) OCCURS 100 TIMES.
    01 Result                PIC S9(9) OCCURS 100 TIMES.

PROCEDURE DIVISION USING R, My-List, Result.
  PERFORM UNTIL R > 10
    CALL Cons USING BY CONTENT R, My-List BY REFERENCE My-List
    COMPUTE R = R + 1
  END-PERFORM.
  EXIT PROGRAM.

END PROGRAM Cons-My-List.

END PROGRAM Test4.