Program Structure

Program Structure

COBOL programming language has its program structure, like other programming languages, and it should apply to every program written in the COBOL language.

The COBOL program structure is a top-to-bottom hierarchical design and it consists of Divisions, Sections, Paragraphs, Sentences, Statements, and Character strings.

COBOL Program Structure

Let us discuss from the smaller element to the larger one for a better understanding.

Character Set -

The character set refers to the collection of valid characters that can be used within the language. It is used to define literals, variables, and other identifiers in a COBOL program. We have discussed about this verb in the previous topic.

Character Strings -

Character strings refer to sequences of characters that consist of letters, digits, spaces, and special characters. These are often used as literals, variables, keywords, etc. For example - WS-VAR, ZEROES, MOVE, IF, DISPLAY, etc.

Statements -

  • Statements are specific instructions used within the PROCEDURE DIVISION to define the operations that the program will perform on data. Statements decide the program's flow, data manipulations, input/output operations, and many more.
  • The statement is a combination of COBOL keywords and operands, and it should have at least one COBOL keyword.
  • All statements should be coded in Area-B in the PROCEDURE DIVISION and is marked with a period(.) at the end.
  • COBOL statements are divided into four types based on their usage, and those are -
    • Imperative Statements
    • Conditional Statements
    • Delimited scope Statements
    • Compiler directing Statements

For example - Two statements in a program.

----+----1----+----2----+----3----+----4----+----5
       IDENTIFICATION DIVISION.
       PROGRAM-ID. PROGSTRU.
	   AUTHOR. MTH.

       PROCEDURE DIVISION.
       1000-SEC1 SECTION.
       1000-PARA.
           DISPLAY "Hello World".      --> Statement1    
           DISPLAY "Welcome to MTH".   --> Statement2          
           STOP RUN.

Sentences -

  • A sentence is a sequence of one or more statements ended by a period (.) within the PROCEDURE DIVISION.
  • Sentences provide a way to group related statements together, and the period indicates the end of that particular logical sequence.
  • If the first statement ends with a period, it is considered a statement but not a sentence.
  • All sentences should be coded in Area-B in the PROCEDURE DIVISION.

For example - A sentence with two statements.

----+----1----+----2----+----3----+----4----+----5
       IDENTIFICATION DIVISION.
       PROGRAM-ID. PROGSTRU.
	   AUTHOR. MTH.

       PROCEDURE DIVISION.
       1000-SEC1 SECTION.
       1000-PARA.
           DISPLAY "Hello World"       --]   
           DISPLAY "Welcome to MTH".   --]--> Sentence          
           STOP RUN.

Paragraphs -

  • A paragraph is a block of code within the PROCEDURE DIVISION consisting of one or more sentences. It represents a specific unit of logic or functionality and can be directly called or performed by other parts of the program.
  • A paragraph begins with the paragraph name and ends when any of the following is met -
    • The scope terminator of the same paragraph.
    • Starting of another paragraph.
    • Beginning of the new section.
    • The program ends.
  • All paragraph names should code in Area-A and the logical code in it should code in Area-B.

For example - A paragraph in the program.

----+----1----+----2----+----3----+----4----+----5
       IDENTIFICATION DIVISION.
       PROGRAM-ID. PROGSTRU.
	   AUTHOR. MTH.

       PROCEDURE DIVISION.
       1000-SEC1 SECTION.
       1000-PARA.                --> Paragraph
           DISPLAY "Hello World" 
           DISPLAY "Welcome to MTH".         
           STOP RUN.

Sections -

  • A section is a collection of one or more related paragraphs within the PROCEDURE DIVISION.
  • Sections are coded by a name followed by the keyword SECTION. It ends at another section starting or ending the program.
  • When the section can be performed or called in the program, it executes all the paragraphs within that section sequentially.
  • All section names should code in Area-A, and the code in it should code in Area-B.

For example - Sections in the program.

----+----1----+----2----+----3----+----4----+----5
       IDENTIFICATION DIVISION.
       PROGRAM-ID. PROGSTRU.
	   AUTHOR. MTH.

       PROCEDURE DIVISION.
       1000-SEC1 SECTION.     --> Section
       1000-PARA.
           DISPLAY "Hello World" 
           DISPLAY "Welcome to MTH".         
           STOP RUN.

Divisions -

  • A division is one of the primary parts of a program, organizing its content and functionality. A division is a collection of one or more sections and paragraphs.
  • Division begins with the division name and ends at the beginning of the subsequent division or the program ends.
  • All divisions are system-defined and should begin in Area-A.
  • COBOL has four system-defined divisions, and those are -
    • IDENTIFICATION DIVISION (program metadata).
    • ENVIRONMENT DIVISION (configuration and I/O specifications).
    • DATA DIVISION (data definition).
    • PROCEDURE DIVISION (program logic).

For example - Sections in the program.

----+----1----+----2----+----3----+----4----+----5
       IDENTIFICATION DIVISION.  --> Division
       PROGRAM-ID. PROGSTRU.
	   AUTHOR. MTH.

       PROCEDURE DIVISION.       --> Division
       1000-SEC1 SECTION.
       1000-PARA.
           DISPLAY "Hello World" 
           DISPLAY "Welcome to MTH".         
           STOP RUN.

Syntactical Hierarchy -

Each division has its own set of elements, and the syntactical hierarchy is shown below -

Syntactical Hierarchy