Program Structure

COBOL (Common Business-Oriented Language) is one of the longest-living programming languages in history, designed specifically for business and financial applications. Unlike modern languages, it has a rigid and formal structure split into sections called Divisions.

Fixed Layout and Area Formats

In traditional COBOL source files, every line is divided into specific areas based on columns:

• Columns 1-6 (Sequence Area): Historically used for punch card sequence numbers. Today it is usually left blank.
• Column 7 (Indicator Area): Used to mark comment lines by placing an asterisk *.
• Columns 8-11 (Area A): This is where division, section, and paragraph headers start.
• Columns 12-72 (Area B): This is where actual executable statements (like DISPLAY, MOVE, etc.) are written.
• Columns 73-80 (Identification Area): Historically ignored by the compiler, used for internal identification.

In our exercises, we will use a simplified but consistent formatting by starting Area B instructions with appropriate spaces (usually 7 or 11 spaces depending on the area).

The Four Main Divisions

Every complete COBOL program is structured into four mandatory divisions, which must appear in this exact order:

1. IDENTIFICATION DIVISION. Contains program metadata, such as the program name defined with the PROGRAM-ID keyword.

2. ENVIRONMENT DIVISION. Specifies the environment in which the program runs and maps physical files to internal variables.

3. DATA DIVISION. Where all variables and data structures used by the program are declared.

4. PROCEDURE DIVISION. Contains the executable instructions (the business logic). Every program must end with STOP RUN. to stop execution.

Try it yourself