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COBOL — Interactive Tutorial

A complete COBOL learning path: five levels from your first program to expert internals. Every lesson has runnable examples, a quiz, and coding challenges — all free.

The whole path

60 of 60 lessons written

Foundations

First Steps
  1. Your First COBOL Program
  2. Why COBOL Still Runs the World
  3. The Four Divisions
  4. Fixed Format and the Column Rules
  5. How a COBOL Program Is Built and Run
Declaring Data
  1. PIC: Declaring Data
  2. VALUE and Initial Contents
  3. MOVE and COMPUTE
  4. Formatting Numbers for Humans
  5. Signed Numbers and Overpunch
Control Flow
  1. IF, ELSE and Condition Names
  2. EVALUATE: The Decision Table
  3. PERFORM: Loops and Paragraphs
  4. PERFORM THRU, Inline and Scope
  5. CONTINUE, NEXT SENTENCE and Scope Terminators
  6. Project: A Payslip Calculator

Beginner

Structured Data
  1. Group Items and Record Layouts
  2. OCCURS: Tables
  3. INDEXED BY and SET
  4. SEARCH and SEARCH ALL
  5. Nested OCCURS
  6. REDEFINES: Reinterpreting Storage
  7. RENAMES and USAGE
Working with Text
  1. STRING and UNSTRING
  2. INSPECT: Counting and Replacing
  3. Reference Modification
Files and Batch
  1. Reading and Writing Sequential Files
  2. FILE STATUS and Handling Errors
  3. Producing a Printed Report
  4. Control Break Logic
  5. Project: Sales Report with Totals

Intermediate

Program Structure at Scale
  1. CALL and the LINKAGE SECTION
  2. Static and Dynamic CALL
  3. COPY Books
  4. Nested Programs and GLOBAL
  5. SORT and MERGE
The Mainframe Platform
  1. JCL: How a COBOL Program Gets Run
  2. PROCs, Symbols and Overrides
  3. Datasets: PS, PDS and Members
  4. Indexed Files and VSAM
  5. Relative Files
  6. Return Codes and Job Flow
Correctness
  1. Debugging: DISPLAY, Abends and Dumps
  2. Writing Defensively
  3. Testing COBOL

Advanced

Working in Real Codebases
  1. Reading a Program You Did Not Write
  2. GO TO, ALTER and Structured Programming
  3. Changing Code Without Breaking It
  4. COMP, COMP-3 and Packed Decimal
  5. Converting Between Representations
Integration
  1. COBOL and DB2: Embedded SQL
  2. Cursors and Result Sets
  3. CICS: Online COBOL
  4. APIs, JSON and the Outside World

Expert

Mastery
  1. What Changed: COBOL 2002 and 2014
  2. Intrinsic Functions
  3. Performance in Batch
  4. Designing a Large COBOL System
  5. The Interview: What They Actually Ask
  6. Capstone: A Complete Batch Payroll System