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.

COBOL program structure is a top-to-bottom hierarchical design, consisting 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 -

  • 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 this verb in the previous topic.

Character Strings -

  • Character strings are sequences of characters that consist of letters, digits, spaces, and special characters.
  • They are also known as literals, variables, keywords, etc.
  • For example - WS-VAR, ZEROES, MOVE, IF, DISPLAY, etc.

Statements -

  • A COBOL statement is a combination of COBOL keywords and operands. It's important to note that a statement should always include at least one COBOL keyword, as these keywords are the building blocks of the COBOL programming language.
  • Statements decide the program's flow, data manipulations, input/output operations, etc.
  • All statements should code in Area-B of the PROCEDURE DIVISION.
  • All statements should mark with a explicit scope terminator (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 two or more statements ended by a period (.).
  • It provides a way to group related statements together, and the explicit scope terminator (period) indicates the end of the sentence.
  • 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 of 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 consisting of one or more sentences or statements.
  • It represents a logical code unit and can be called or performed by other parts of the program.
  • A paragraph coding begins with the paragraph name and ends when any of the following meets -
    • Scope terminator of the same paragraph.
    • Starting of another paragraph.
    • Beginning of the new section.
    • The program ends.
  • All paragraph names should be coded in Area A, and its code should be 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 is called in the program, it executes all its paragraphs sequentially.
  • All section names should be coded in Area A and their 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 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 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