SECTIONs in COBOL can be required or optional, depending on which DIVISION they are in.

DATA DIVISION.
FILE SECTION.
FD SAMPLE-FILE
01 FILE-NAME PIC X(20).
WORKING-STORAGE SECTION.
01 WS-STUDENT PIC A(10).
01 WS-ID PIC 9(5).
LOCAL-STORAGE SECTION.
01 LS-CLASS PIC 9(3).
LINKAGE SECTION.
01 LS-ID PIC 9(5).

In the above example, 01's are level numbers.

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Level Number

Level number is used to specify the level of data in a record. They are used to differentiate between elementary items and group items. Elementary items can be grouped together to create group items.

• 01: Record description entry. Group level number is always 01.

DATA DIVISION.
WORKING-STORAGE SECTION.
01 WS-NAME               PIC X(25).   ---> ELEMENTARY ITEM 
01 WS-SURNAME            PIC X(25).   ---> ELEMENTARY ITEM    
01 WS-ADDRESS.                        ---> GROUP ITEM   
   05 WS-HOUSE-NUMBER    PIC 9(3).    ---> ELEMENTARY ITEM
   05 WS-STREET          PIC X(15).   ---> ELEMENTARY ITEM 

• 02 to 49: Elementary items
• 66: Rename Clause items
• 77: Items which cannot be sub-divided.
• 88: Level 88 is a special level number used to improve the readability of COBOL programs and to improve IF tests. A level 88 looks like a level under another variable, but it's not. It does not have a PICTURE, but it does have a value. A level 88 is always associated with another variable and is a condition name for that variable.

 01 YES-NO PIC X.
 88 ANSWER-IS-YES VALUE "Y".

Both of the following conditions test whether YES-NO is equal to "Y":

 IF YES-NO = "Y"
 IF ANSWER-IS-YES

A level 88 condition name can be used for an alphanumeric or numeric variable.

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Picture Clause

The PICTURE CLAUSE defines two things about a variable: the size of the variable (the number of bytes used in memory for the value) and the type of data that can be stored in the variable.