Error using OCCURS in a very simple COBOL program

Question

This is my code where iIam declaring a variable using OCCURS.

   IDENTIFICATION DIVISION.
   PROGRAM-ID. ARRAYEX.

   ENVIRONMENT DIVISION.
   INPUT-OUTPUT SECTION.
   FILE-CONTROL.
        SELECT StudentFile ASSIGN TO "STUDENTS.DAT"
            ORGANIZATION IS LINE SEQUENTIAL.

   DATA DIVISION.
   WORKING-STORAGE SECTION.
   77 WS-FIRSTARR OCCURS 10 TIMES PIC 9(5).

   PROCEDURE DIVISION.

   DISPLAY "HELLO WORLD".
   STOP RUN.

Error:

arrayex.cbl:12: Error: Level 77 item 'WS-FIRSTARR' cannot have OCCURS clause

Any reasons the compilation fails?

Answer 1

A 77 cannot have OCCURS. An 01 cannot have OCCURS. Levels 02-49 can have OCCURS.

Forget level 66 (used for the RENAMES clause) as your should not use it and are unlikely to ever see it.

An 88-level, a Condition Name, cannot have an occurs, but if the field which it is defined on is part of an OCCURS or subordinate to an OCCURS, the 88 will need subscripting like any 02- - 49-level which is also part of, or subordinate to, an OCCURS.

01  a-simple-array-structure.
    05  the-data occurs 5 times           pic 9(5).

Or you can get more complex.

01  b-structure.
    95  the-key                           pic x(8).
    05  some-data                         pic x(10).
    05  some-more-data                    pic 9(7).
    05  a-simple-array.
        10  a-simple-array-item occurs 5 times       
                                          pic 9(5).
    05  a-more-complex-array.
        10  complex-entry occurs 10 times.
            15  some-complex-data         pic xx.
            15  another-bit-of-complex-data
                                          pic 9(5).

OCCURS can also be used to define multi-dimensional tables.

    05  first-occurs occurs 5 times.
        10  second-occurs occurs 5 times.
            15  an-item                   pic xx.

This is still far from the full gamut of OCCURS, so start simple, practice, get it working, become more complex.

There is also OCCURS DEPENDING ON, a variable-length table. One thing at a time. Get a simple OCCURS working, not just the definition, but the use as well, with a field for a subscript, an index for a subscript and a literal for a subscript.

Then get more complex.