MainframeMaster

COBOL Code Readability

Code readability is fundamental to writing maintainable COBOL programs. Readable code is easier to understand, debug, modify, and maintain, reducing the time and effort required for future development work. Good readability practices make COBOL programs more accessible to both current and future developers.

Understanding Code Readability

Readable code follows consistent patterns, uses clear and descriptive names, includes meaningful comments, and is organized in a logical manner. The goal is to make the code self-documenting so that anyone reading it can quickly understand its purpose, structure, and functionality without extensive external documentation.

Naming Conventions

1. Descriptive Variable Names

Variable names should clearly describe what the data represents and how it's used in the program. Good names make the code self-documenting and reduce the need for additional comments to explain what variables contain or represent.

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       IDENTIFICATION DIVISION.
       PROGRAM-ID. READABLE-NAMING-EXAMPLE.
       *> This program demonstrates good naming conventions for readability
       
       DATA DIVISION.
       WORKING-STORAGE SECTION.
       *> Good naming: descriptive and clear
       01 CUSTOMER-ACCOUNT-DATA.
           05 CUSTOMER-ACCOUNT-NUMBER    PIC 9(10).
           05 CUSTOMER-FULL-NAME        PIC X(50).
           05 CUSTOMER-ACCOUNT-BALANCE  PIC 9(10)V99.
           05 CUSTOMER-ACCOUNT-TYPE     PIC X(1).
               88 CHECKING-ACCOUNT      VALUE 'C'.
               88 SAVINGS-ACCOUNT       VALUE 'S'.
               88 BUSINESS-ACCOUNT      VALUE 'B'.
       
       *> Good naming: indicates purpose and usage
       01 TRANSACTION-PROCESSING-CONTROLS.
           05 CURRENT-TRANSACTION-AMOUNT PIC 9(8)V99.
           05 TRANSACTION-PROCESSING-STATUS PIC X(1).
               88 TRANSACTION-SUCCESSFUL VALUE 'S'.
               88 TRANSACTION-FAILED     VALUE 'F'.
           05 TRANSACTION-ERROR-MESSAGE PIC X(100).
       
       *> Good naming: shows data relationships
       01 ACCOUNT-BALANCE-CALCULATIONS.
           05 PREVIOUS-ACCOUNT-BALANCE  PIC 9(10)V99.
           05 TRANSACTION-AMOUNT        PIC 9(8)V99.
           05 NEW-ACCOUNT-BALANCE       PIC 9(10)V99.
           05 BALANCE-CHANGE-AMOUNT     PIC S9(8)V99.
       
       PROCEDURE DIVISION.
       MAIN-PROCESSING-LOGIC.
           DISPLAY 'Starting customer account processing...'
           
       *> Clear procedure names that describe their function
           PERFORM INITIALIZE-CUSTOMER-ACCOUNT-DATA
           PERFORM VALIDATE-CUSTOMER-ACCOUNT-INPUT
           PERFORM PROCESS-CUSTOMER-TRANSACTION
           PERFORM UPDATE-CUSTOMER-ACCOUNT-BALANCE
           PERFORM DISPLAY-TRANSACTION-RESULTS
           
           STOP RUN.
       
       INITIALIZE-CUSTOMER-ACCOUNT-DATA.
       *> Procedure name clearly indicates what it does
           MOVE ZERO TO CUSTOMER-ACCOUNT-NUMBER
           MOVE SPACES TO CUSTOMER-FULL-NAME
           MOVE ZERO TO CUSTOMER-ACCOUNT-BALANCE
           MOVE 'C' TO CUSTOMER-ACCOUNT-TYPE
           MOVE 'S' TO TRANSACTION-PROCESSING-STATUS
           MOVE SPACES TO TRANSACTION-ERROR-MESSAGE
           
           DISPLAY 'Customer account data initialized'.
       
       VALIDATE-CUSTOMER-ACCOUNT-INPUT.
       *> Clear validation procedure with descriptive name
           IF CUSTOMER-ACCOUNT-NUMBER = 0
               MOVE 'F' TO TRANSACTION-PROCESSING-STATUS
               MOVE 'Customer account number is required' TO TRANSACTION-ERROR-MESSAGE
           ELSE
               IF CUSTOMER-FULL-NAME = SPACES
                   MOVE 'F' TO TRANSACTION-PROCESSING-STATUS
                   MOVE 'Customer name is required' TO TRANSACTION-ERROR-MESSAGE
               ELSE
                   IF CUSTOMER-ACCOUNT-BALANCE < 0
                       MOVE 'F' TO TRANSACTION-PROCESSING-STATUS
                       MOVE 'Account balance cannot be negative' TO TRANSACTION-ERROR-MESSAGE
                   END-IF
               END-IF
           END-IF.
       
       PROCESS-CUSTOMER-TRANSACTION.
       *> Descriptive procedure name for transaction processing
           IF TRANSACTION-SUCCESSFUL
               PERFORM CALCULATE-NEW-ACCOUNT-BALANCE
               PERFORM VALIDATE-ACCOUNT-BALANCE-LIMITS
           END-IF.
       
       CALCULATE-NEW-ACCOUNT-BALANCE.
       *> Clear calculation procedure
           MOVE CUSTOMER-ACCOUNT-BALANCE TO PREVIOUS-ACCOUNT-BALANCE
           MOVE 100.00 TO TRANSACTION-AMOUNT
           ADD TRANSACTION-AMOUNT TO CUSTOMER-ACCOUNT-BALANCE
           MOVE CUSTOMER-ACCOUNT-BALANCE TO NEW-ACCOUNT-BALANCE
           COMPUTE BALANCE-CHANGE-AMOUNT = NEW-ACCOUNT-BALANCE - PREVIOUS-ACCOUNT-BALANCE.
       
       VALIDATE-ACCOUNT-BALANCE-LIMITS.
       *> Clear validation procedure for balance limits
           IF CHECKING-ACCOUNT
               IF CUSTOMER-ACCOUNT-BALANCE > 100000.00
                   MOVE 'F' TO TRANSACTION-PROCESSING-STATUS
                   MOVE 'Checking account balance exceeds limit' TO TRANSACTION-ERROR-MESSAGE
               END-IF
           ELSE
               IF SAVINGS-ACCOUNT
                   IF CUSTOMER-ACCOUNT-BALANCE > 500000.00
                       MOVE 'F' TO TRANSACTION-PROCESSING-STATUS
                       MOVE 'Savings account balance exceeds limit' TO TRANSACTION-ERROR-MESSAGE
                   END-IF
               END-IF
           END-IF.
       
       UPDATE-CUSTOMER-ACCOUNT-BALANCE.
       *> Clear update procedure
           IF TRANSACTION-SUCCESSFUL
               DISPLAY 'Account balance updated successfully'
           ELSE
               DISPLAY 'Account balance update failed: ' TRANSACTION-ERROR-MESSAGE
           END-IF.
       
       DISPLAY-TRANSACTION-RESULTS.
       *> Clear display procedure
           DISPLAY 'Transaction Processing Results:'
           DISPLAY 'Customer Account: ' CUSTOMER-ACCOUNT-NUMBER
           DISPLAY 'Customer Name: ' CUSTOMER-FULL-NAME
           DISPLAY 'Previous Balance: ' PREVIOUS-ACCOUNT-BALANCE
           DISPLAY 'Transaction Amount: ' TRANSACTION-AMOUNT
           DISPLAY 'New Balance: ' NEW-ACCOUNT-BALANCE
           DISPLAY 'Balance Change: ' BALANCE-CHANGE-AMOUNT.

This example demonstrates excellent naming conventions that make the code self-documenting. Variable names like CUSTOMER-ACCOUNT-NUMBER and TRANSACTION-PROCESSING-STATUS clearly indicate their purpose and usage. Procedure names like VALIDATE-CUSTOMER-ACCOUNT-INPUT and CALCULATE-NEW-ACCOUNT-BALANCE describe exactly what each section does. This approach makes the code much easier to understand and maintain.

2. Consistent Naming Patterns

Consistent naming patterns help developers quickly understand the structure and relationships in the code. Using prefixes, suffixes, and consistent word ordering makes it easier to locate related variables and understand their purpose.

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       IDENTIFICATION DIVISION.
       PROGRAM-ID. CONSISTENT-NAMING-PATTERNS.
       *> This program demonstrates consistent naming patterns
       
       DATA DIVISION.
       WORKING-STORAGE SECTION.
       *> Consistent prefix pattern: CUSTOMER- for all customer-related data
       01 CUSTOMER-MASTER-RECORD.
           05 CUSTOMER-ID              PIC 9(8).
           05 CUSTOMER-NAME            PIC X(50).
           05 CUSTOMER-ADDRESS         PIC X(100).
           05 CUSTOMER-PHONE           PIC X(15).
           05 CUSTOMER-EMAIL           PIC X(100).
           05 CUSTOMER-CREATION-DATE   PIC X(10).
           05 CUSTOMER-LAST-UPDATE-DATE PIC X(10).
       
       *> Consistent prefix pattern: ACCOUNT- for all account-related data
       01 ACCOUNT-DETAILS-RECORD.
           05 ACCOUNT-NUMBER           PIC 9(10).
           05 ACCOUNT-TYPE             PIC X(1).
           05 ACCOUNT-BALANCE          PIC 9(10)V99.
           05 ACCOUNT-OPEN-DATE        PIC X(10).
           05 ACCOUNT-STATUS           PIC X(1).
           05 ACCOUNT-CREDIT-LIMIT     PIC 9(8)V99.
       
       *> Consistent suffix pattern: -COUNT for all counter variables
       01 PROCESSING-STATISTICS.
           05 TOTAL-RECORDS-COUNT      PIC 9(6).
           05 VALID-RECORDS-COUNT      PIC 9(6).
           05 ERROR-RECORDS-COUNT      PIC 9(6).
           05 PROCESSED-RECORDS-COUNT  PIC 9(6).
       
       *> Consistent suffix pattern: -FLAG for all boolean indicators
       01 PROCESSING-CONTROL-FLAGS.
           05 END-OF-FILE-FLAG         PIC X(1).
               88 END-OF-FILE          VALUE 'Y'.
               88 NOT-END-OF-FILE      VALUE 'N'.
           05 VALIDATION-ERROR-FLAG    PIC X(1).
               88 VALIDATION-ERROR     VALUE 'Y'.
               88 NO-VALIDATION-ERROR  VALUE 'N'.
           05 PROCESSING-COMPLETE-FLAG PIC X(1).
               88 PROCESSING-COMPLETE  VALUE 'Y'.
               88 PROCESSING-INCOMPLETE VALUE 'N'.
       
       *> Consistent pattern: -MESSAGE for all error messages
       01 ERROR-MESSAGES.
           05 FILE-ERROR-MESSAGE       PIC X(100).
           05 VALIDATION-ERROR-MESSAGE PIC X(100).
           05 PROCESSING-ERROR-MESSAGE PIC X(100).
           05 SYSTEM-ERROR-MESSAGE     PIC X(100).
       
       PROCEDURE DIVISION.
       MAIN-PROCESSING-ROUTINE.
       *> Consistent procedure naming: descriptive action names
           PERFORM INITIALIZE-PROCESSING-VARIABLES
           PERFORM OPEN-INPUT-FILES
           PERFORM PROCESS-ALL-RECORDS
           PERFORM CLOSE-INPUT-FILES
           PERFORM DISPLAY-PROCESSING-STATISTICS
           
           STOP RUN.
       
       INITIALIZE-PROCESSING-VARIABLES.
       *> Consistent initialization pattern
           MOVE ZERO TO TOTAL-RECORDS-COUNT
           MOVE ZERO TO VALID-RECORDS-COUNT
           MOVE ZERO TO ERROR-RECORDS-COUNT
           MOVE ZERO TO PROCESSED-RECORDS-COUNT
           SET NOT-END-OF-FILE TO TRUE
           SET NO-VALIDATION-ERROR TO TRUE
           SET PROCESSING-INCOMPLETE TO TRUE
           MOVE SPACES TO FILE-ERROR-MESSAGE
           MOVE SPACES TO VALIDATION-ERROR-MESSAGE
           MOVE SPACES TO PROCESSING-ERROR-MESSAGE
           MOVE SPACES TO SYSTEM-ERROR-MESSAGE.
       
       OPEN-INPUT-FILES.
       *> Consistent file operation naming
           DISPLAY 'Opening input files...'
           *> File opening logic would go here.
       
       PROCESS-ALL-RECORDS.
       *> Consistent processing pattern
           PERFORM UNTIL END-OF-FILE
               PERFORM READ-NEXT-RECORD
               IF NOT-END-OF-FILE
                   PERFORM VALIDATE-RECORD-DATA
                   IF NO-VALIDATION-ERROR
                       PERFORM PROCESS-VALID-RECORD
                   ELSE
                       PERFORM HANDLE-VALIDATION-ERROR
                   END-IF
               END-IF
           END-PERFORM.
       
       READ-NEXT-RECORD.
       *> Consistent I/O operation naming
           ADD 1 TO TOTAL-RECORDS-COUNT
           *> Record reading logic would go here.
       
       VALIDATE-RECORD-DATA.
       *> Consistent validation naming
           IF CUSTOMER-ID = 0
               SET VALIDATION-ERROR TO TRUE
               MOVE 'Invalid customer ID' TO VALIDATION-ERROR-MESSAGE
           ELSE
               IF CUSTOMER-NAME = SPACES
                   SET VALIDATION-ERROR TO TRUE
                   MOVE 'Customer name is required' TO VALIDATION-ERROR-MESSAGE
               END-IF
           END-IF.
       
       PROCESS-VALID-RECORD.
       *> Consistent processing naming
           ADD 1 TO VALID-RECORDS-COUNT
           ADD 1 TO PROCESSED-RECORDS-COUNT
           *> Record processing logic would go here.
       
       HANDLE-VALIDATION-ERROR.
       *> Consistent error handling naming
           ADD 1 TO ERROR-RECORDS-COUNT
           DISPLAY 'Validation error: ' VALIDATION-ERROR-MESSAGE.
       
       CLOSE-INPUT-FILES.
       *> Consistent file operation naming
           DISPLAY 'Closing input files...'
           *> File closing logic would go here.
       
       DISPLAY-PROCESSING-STATISTICS.
       *> Consistent display naming
           DISPLAY 'Processing Statistics:'
           DISPLAY 'Total records: ' TOTAL-RECORDS-COUNT
           DISPLAY 'Valid records: ' VALID-RECORDS-COUNT
           DISPLAY 'Error records: ' ERROR-RECORDS-COUNT
           DISPLAY 'Processed records: ' PROCESSED-RECORDS-COUNT.

This example shows consistent naming patterns that make the code structure immediately clear. All customer-related variables use the CUSTOMER- prefix, all counters use the -COUNT suffix, all flags use the -FLAG suffix, and all error messages use the -MESSAGE suffix. This consistency helps developers quickly understand relationships and locate related variables throughout the program.

Code Structure and Organization

1. Logical Procedure Organization

Organizing procedures in a logical order that follows the natural flow of the business process makes the code easier to follow and understand. Related procedures should be grouped together, and the main procedure should provide a clear overview of the program's structure.

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       IDENTIFICATION DIVISION.
       PROGRAM-ID. WELL-ORGANIZED-STRUCTURE.
       *> This program demonstrates logical procedure organization
       
       DATA DIVISION.
       WORKING-STORAGE SECTION.
       01 CUSTOMER-PROCESSING-DATA.
           05 CUSTOMER-RECORD-COUNT    PIC 9(6) VALUE 0.
           05 PROCESSING-STATUS        PIC X(1).
               88 PROCESSING-SUCCESS   VALUE 'S'.
               88 PROCESSING-FAILURE   VALUE 'F'.
       
       PROCEDURE DIVISION.
       *> Main procedure provides clear program overview
       MAIN-CUSTOMER-PROCESSING.
           DISPLAY 'Starting Customer Processing System'
           
       *> Logical flow: Initialize -> Process -> Validate -> Update -> Report
           PERFORM INITIALIZE-CUSTOMER-PROCESSING
           PERFORM PROCESS-CUSTOMER-RECORDS
           PERFORM VALIDATE-PROCESSING-RESULTS
           PERFORM UPDATE-CUSTOMER-DATABASE
           PERFORM GENERATE-PROCESSING-REPORT
           PERFORM CLEANUP-PROCESSING-RESOURCES
           
           DISPLAY 'Customer Processing System Completed'
           STOP RUN.
       
       *> ========================================
       *> INITIALIZATION SECTION
       *> ========================================
       INITIALIZE-CUSTOMER-PROCESSING.
       *> Grouped initialization procedures
           PERFORM INITIALIZE-PROCESSING-VARIABLES
           PERFORM INITIALIZE-FILE-HANDLES
           PERFORM INITIALIZE-ERROR-HANDLING
           PERFORM VALIDATE-SYSTEM-ENVIRONMENT.
       
       INITIALIZE-PROCESSING-VARIABLES.
           MOVE 0 TO CUSTOMER-RECORD-COUNT
           SET PROCESSING-SUCCESS TO TRUE
           DISPLAY 'Processing variables initialized'.
       
       INITIALIZE-FILE-HANDLES.
           DISPLAY 'Initializing file handles...'
           *> File initialization logic.
       
       INITIALIZE-ERROR-HANDLING.
           DISPLAY 'Initializing error handling...'
           *> Error handling setup.
       
       VALIDATE-SYSTEM-ENVIRONMENT.
           DISPLAY 'Validating system environment...'
           *> Environment validation.
       
       *> ========================================
       *> PROCESSING SECTION
       *> ========================================
       PROCESS-CUSTOMER-RECORDS.
       *> Grouped processing procedures
           PERFORM OPEN-CUSTOMER-FILES
           PERFORM READ-AND-PROCESS-RECORDS
           PERFORM CLOSE-CUSTOMER-FILES.
       
       OPEN-CUSTOMER-FILES.
           DISPLAY 'Opening customer files...'
           *> File opening logic.
       
       READ-AND-PROCESS-RECORDS.
           PERFORM UNTIL END-OF-FILE
               PERFORM READ-NEXT-CUSTOMER-RECORD
               IF NOT-END-OF-FILE
                   PERFORM VALIDATE-CUSTOMER-RECORD
                   IF RECORD-VALID
                       PERFORM PROCESS-CUSTOMER-RECORD
                   ELSE
                       PERFORM HANDLE-INVALID-RECORD
                   END-IF
               END-IF
           END-PERFORM.
       
       READ-NEXT-CUSTOMER-RECORD.
           ADD 1 TO CUSTOMER-RECORD-COUNT
           *> Record reading logic.
       
       VALIDATE-CUSTOMER-RECORD.
       *> Grouped validation procedures
           PERFORM VALIDATE-CUSTOMER-ID
           PERFORM VALIDATE-CUSTOMER-NAME
           PERFORM VALIDATE-CUSTOMER-ADDRESS
           PERFORM VALIDATE-CUSTOMER-PHONE.
       
       VALIDATE-CUSTOMER-ID.
           IF CUSTOMER-ID = 0
               SET RECORD-INVALID TO TRUE
           END-IF.
       
       VALIDATE-CUSTOMER-NAME.
           IF CUSTOMER-NAME = SPACES
               SET RECORD-INVALID TO TRUE
           END-IF.
       
       VALIDATE-CUSTOMER-ADDRESS.
           IF CUSTOMER-ADDRESS = SPACES
               SET RECORD-INVALID TO TRUE
           END-IF.
       
       VALIDATE-CUSTOMER-PHONE.
           IF CUSTOMER-PHONE = SPACES
               SET RECORD-INVALID TO TRUE
           END-IF.
       
       PROCESS-CUSTOMER-RECORD.
       *> Grouped processing procedures
           PERFORM CALCULATE-CUSTOMER-STATISTICS
           PERFORM UPDATE-CUSTOMER-FIELDS
           PERFORM WRITE-CUSTOMER-RECORD.
       
       CALCULATE-CUSTOMER-STATISTICS.
           *> Statistics calculation logic.
       
       UPDATE-CUSTOMER-FIELDS.
           *> Field update logic.
       
       WRITE-CUSTOMER-RECORD.
           *> Record writing logic.
       
       HANDLE-INVALID-RECORD.
           DISPLAY 'Invalid record encountered'
           *> Error handling logic.
       
       CLOSE-CUSTOMER-FILES.
           DISPLAY 'Closing customer files...'
           *> File closing logic.
       
       *> ========================================
       *> VALIDATION SECTION
       *> ========================================
       VALIDATE-PROCESSING-RESULTS.
       *> Grouped validation procedures
           PERFORM VALIDATE-RECORD-COUNTS
           PERFORM VALIDATE-PROCESSING-STATUS
           PERFORM VALIDATE-SYSTEM-INTEGRITY.
       
       VALIDATE-RECORD-COUNTS.
           IF CUSTOMER-RECORD-COUNT = 0
               SET PROCESSING-FAILURE TO TRUE
           END-IF.
       
       VALIDATE-PROCESSING-STATUS.
           *> Status validation logic.
       
       VALIDATE-SYSTEM-INTEGRITY.
           *> System integrity checks.
       
       *> ========================================
       *> UPDATE SECTION
       *> ========================================
       UPDATE-CUSTOMER-DATABASE.
       *> Grouped update procedures
           PERFORM BACKUP-CURRENT-DATABASE
           PERFORM APPLY-CUSTOMER-UPDATES
           PERFORM VERIFY-DATABASE-INTEGRITY.
       
       BACKUP-CURRENT-DATABASE.
           DISPLAY 'Backing up current database...'
           *> Backup logic.
       
       APPLY-CUSTOMER-UPDATES.
           DISPLAY 'Applying customer updates...'
           *> Update logic.
       
       VERIFY-DATABASE-INTEGRITY.
           DISPLAY 'Verifying database integrity...'
           *> Integrity verification.
       
       *> ========================================
       *> REPORTING SECTION
       *> ========================================
       GENERATE-PROCESSING-REPORT.
       *> Grouped reporting procedures
           PERFORM CREATE-REPORT-HEADER
           PERFORM GENERATE-REPORT-DATA
           PERFORM FORMAT-REPORT-OUTPUT
           PERFORM DISPLAY-REPORT-RESULTS.
       
       CREATE-REPORT-HEADER.
           DISPLAY 'Creating report header...'
           *> Header creation logic.
       
       GENERATE-REPORT-DATA.
           DISPLAY 'Generating report data...'
           *> Data generation logic.
       
       FORMAT-REPORT-OUTPUT.
           DISPLAY 'Formatting report output...'
           *> Output formatting logic.
       
       DISPLAY-REPORT-RESULTS.
           DISPLAY 'Processing Report:'
           DISPLAY 'Records processed: ' CUSTOMER-RECORD-COUNT
           DISPLAY 'Processing status: ' PROCESSING-STATUS.
       
       *> ========================================
       *> CLEANUP SECTION
       *> ========================================
       CLEANUP-PROCESSING-RESOURCES.
       *> Grouped cleanup procedures
           PERFORM RELEASE-MEMORY-RESOURCES
           PERFORM CLOSE-SYSTEM-FILES
           PERFORM RESET-PROCESSING-FLAGS.
       
       RELEASE-MEMORY-RESOURCES.
           DISPLAY 'Releasing memory resources...'
           *> Memory cleanup logic.
       
       CLOSE-SYSTEM-FILES.
           DISPLAY 'Closing system files...'
           *> File cleanup logic.
       
       RESET-PROCESSING-FLAGS.
           DISPLAY 'Resetting processing flags...'
           *> Flag reset logic.

This example demonstrates excellent code organization with clear section headers and logical grouping of related procedures. The main procedure provides a high-level overview of the program flow, while related procedures are grouped together under descriptive section headers. This organization makes it easy to understand the program structure and locate specific functionality.

2. Meaningful Comments and Documentation

Comments should explain the "why" behind the code, not just the "what". Good comments provide context, explain business logic, document complex algorithms, and help future maintainers understand the reasoning behind implementation decisions.

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       IDENTIFICATION DIVISION.
       PROGRAM-ID. WELL-DOCUMENTED-CODE.
       AUTHOR. DEVELOPMENT-TEAM.
       DATE-WRITTEN. 2024-01-15.
       DATE-COMPILED. 2024-01-15.
       *> ================================================================
       *> PROGRAM PURPOSE:
       *> This program processes customer account transactions and updates
       *> account balances. It handles deposits, withdrawals, and transfers
       *> while maintaining audit trails and ensuring data integrity.
       *> 
       *> BUSINESS RULES:
       *> 1. All transactions must be validated before processing
       *> 2. Account balances cannot go below zero for checking accounts
       *> 3. Savings accounts have a minimum balance requirement of $100
       *> 4. All transactions are logged for audit purposes
       *> 5. Daily transaction limits apply based on account type
       *> ================================================================
       
       DATA DIVISION.
       WORKING-STORAGE SECTION.
       *> ================================================================
       *> CUSTOMER ACCOUNT DATA STRUCTURE
       *> This structure holds all customer account information including
       *> identification, balance, and account type for processing
       *> ================================================================
       01 CUSTOMER-ACCOUNT-INFORMATION.
           05 CUSTOMER-ACCOUNT-NUMBER    PIC 9(10).
           05 CUSTOMER-ACCOUNT-BALANCE   PIC 9(10)V99.
           05 CUSTOMER-ACCOUNT-TYPE      PIC X(1).
               *> Account type codes: C=Checking, S=Savings, B=Business
               88 CHECKING-ACCOUNT-TYPE  VALUE 'C'.
               88 SAVINGS-ACCOUNT-TYPE   VALUE 'S'.
               88 BUSINESS-ACCOUNT-TYPE  VALUE 'B'.
           05 CUSTOMER-DAILY-LIMIT       PIC 9(8)V99.
           05 CUSTOMER-MINIMUM-BALANCE   PIC 9(8)V99.
       
       *> ================================================================
       *> TRANSACTION PROCESSING CONTROLS
       *> These variables control the transaction processing flow and
       *> track the status of various validation and processing steps
       *> ================================================================
       01 TRANSACTION-PROCESSING-CONTROLS.
           05 CURRENT-TRANSACTION-AMOUNT PIC 9(8)V99.
           05 TRANSACTION-TYPE-CODE      PIC X(1).
               *> Transaction type codes: D=Deposit, W=Withdrawal, T=Transfer
               88 DEPOSIT-TRANSACTION    VALUE 'D'.
               88 WITHDRAWAL-TRANSACTION VALUE 'W'.
               88 TRANSFER-TRANSACTION   VALUE 'T'.
           05 TRANSACTION-PROCESSING-STATUS PIC X(1).
               88 TRANSACTION-APPROVED   VALUE 'A'.
               88 TRANSACTION-REJECTED   VALUE 'R'.
               88 TRANSACTION-PENDING    VALUE 'P'.
           05 TRANSACTION-ERROR-CODE     PIC X(2).
               88 NO-ERROR               VALUE '00'.
               88 INSUFFICIENT-FUNDS     VALUE '01'.
               88 EXCEEDS-DAILY-LIMIT    VALUE '02'.
               88 INVALID-ACCOUNT-TYPE   VALUE '03'.
               88 BELOW-MINIMUM-BALANCE  VALUE '04'.
       
       PROCEDURE DIVISION.
       *> ================================================================
       *> MAIN PROCESSING LOGIC
       *> This is the primary entry point that orchestrates the entire
       *> transaction processing workflow
       *> ================================================================
       MAIN-TRANSACTION-PROCESSING.
           DISPLAY 'Starting Transaction Processing System'
           
       *> Initialize all processing variables and validate system state
           PERFORM INITIALIZE-TRANSACTION-PROCESSING
           
       *> Process the transaction through validation and approval steps
           PERFORM PROCESS-CUSTOMER-TRANSACTION
           
       *> Update account balances and create audit records
           PERFORM UPDATE-ACCOUNT-AND-AUDIT-TRAIL
           
       *> Generate processing results and error reports
           PERFORM GENERATE-TRANSACTION-RESULTS
           
           DISPLAY 'Transaction Processing System Completed'
           STOP RUN.
       
       *> ================================================================
       *> INITIALIZATION PROCEDURES
       *> These procedures set up the processing environment and validate
       *> that all required systems and data are available
       *> ================================================================
       INITIALIZE-TRANSACTION-PROCESSING.
       *> Set up all processing variables with default values
           MOVE ZERO TO CUSTOMER-ACCOUNT-NUMBER
           MOVE ZERO TO CUSTOMER-ACCOUNT-BALANCE
           MOVE 'C' TO CUSTOMER-ACCOUNT-TYPE
           MOVE ZERO TO CURRENT-TRANSACTION-AMOUNT
           MOVE 'D' TO TRANSACTION-TYPE-CODE
           SET TRANSACTION-PENDING TO TRUE
           SET NO-ERROR TO TRUE
           
       *> Set account-specific limits based on account type
           PERFORM SET-ACCOUNT-TYPE-LIMITS
           
           DISPLAY 'Transaction processing initialized successfully'.
       
       SET-ACCOUNT-TYPE-LIMITS.
       *> Configure daily limits and minimum balances based on account type
       *> This implements business rules for different account types
           EVALUATE CUSTOMER-ACCOUNT-TYPE
               WHEN 'C'  *> Checking account limits
                   MOVE 5000.00 TO CUSTOMER-DAILY-LIMIT
                   MOVE 0.00 TO CUSTOMER-MINIMUM-BALANCE
               WHEN 'S'  *> Savings account limits
                   MOVE 10000.00 TO CUSTOMER-DAILY-LIMIT
                   MOVE 100.00 TO CUSTOMER-MINIMUM-BALANCE
               WHEN 'B'  *> Business account limits
                   MOVE 50000.00 TO CUSTOMER-DAILY-LIMIT
                   MOVE 1000.00 TO CUSTOMER-MINIMUM-BALANCE
               WHEN OTHER
                   SET INVALID-ACCOUNT-TYPE TO TRUE
           END-EVALUATE.
       
       *> ================================================================
       *> TRANSACTION PROCESSING PROCEDURES
       *> These procedures handle the core business logic for processing
       *> different types of transactions with appropriate validations
       *> ================================================================
       PROCESS-CUSTOMER-TRANSACTION.
       *> Main transaction processing logic that coordinates all validation
       *> and processing steps for the current transaction
           
       *> First, validate the transaction meets basic requirements
           PERFORM VALIDATE-TRANSACTION-BASIC-REQUIREMENTS
           
       *> If basic validation passes, perform account-specific validations
           IF TRANSACTION-APPROVED
               PERFORM VALIDATE-ACCOUNT-SPECIFIC-REQUIREMENTS
           END-IF
           
       *> If all validations pass, process the transaction
           IF TRANSACTION-APPROVED
               PERFORM EXECUTE-TRANSACTION-PROCESSING
           END-IF.
       
       VALIDATE-TRANSACTION-BASIC-REQUIREMENTS.
       *> Validate that the transaction meets fundamental requirements
       *> such as valid account number, positive amount, etc.
           
           IF CUSTOMER-ACCOUNT-NUMBER = 0
               SET TRANSACTION-REJECTED TO TRUE
               SET INVALID-ACCOUNT-TYPE TO TRUE
               DISPLAY 'ERROR: Invalid account number'
           ELSE
               IF CURRENT-TRANSACTION-AMOUNT <= 0
                   SET TRANSACTION-REJECTED TO TRUE
                   SET NO-ERROR TO TRUE  *> Generic validation error
                   DISPLAY 'ERROR: Transaction amount must be positive'
               ELSE
                   SET TRANSACTION-APPROVED TO TRUE
                   DISPLAY 'Basic transaction validation passed'
               END-IF
           END-IF.
       
       VALIDATE-ACCOUNT-SPECIFIC-REQUIREMENTS.
       *> Perform validations specific to the account type and transaction
       *> This includes balance checks, daily limits, and minimum balance
       *> requirements based on business rules
           
           EVALUATE TRANSACTION-TYPE-CODE
               WHEN 'W'  *> Withdrawal validations
                   PERFORM VALIDATE-WITHDRAWAL-REQUIREMENTS
               WHEN 'D'  *> Deposit validations (usually minimal)
                   PERFORM VALIDATE-DEPOSIT-REQUIREMENTS
               WHEN 'T'  *> Transfer validations
                   PERFORM VALIDATE-TRANSFER-REQUIREMENTS
               WHEN OTHER
                   SET TRANSACTION-REJECTED TO TRUE
                   DISPLAY 'ERROR: Invalid transaction type'
           END-EVALUATE.
       
       VALIDATE-WITHDRAWAL-REQUIREMENTS.
       *> Validate withdrawal-specific requirements including sufficient
       *> funds, daily limits, and minimum balance maintenance
           
       *> Check if sufficient funds are available
           IF CURRENT-TRANSACTION-AMOUNT > CUSTOMER-ACCOUNT-BALANCE
               SET TRANSACTION-REJECTED TO TRUE
               SET INSUFFICIENT-FUNDS TO TRUE
               DISPLAY 'ERROR: Insufficient funds for withdrawal'
           ELSE
       *> Check if withdrawal would violate minimum balance requirement
               IF (CUSTOMER-ACCOUNT-BALANCE - CURRENT-TRANSACTION-AMOUNT) 
                  < CUSTOMER-MINIMUM-BALANCE
                   SET TRANSACTION-REJECTED TO TRUE
                   SET BELOW-MINIMUM-BALANCE TO TRUE
                   DISPLAY 'ERROR: Withdrawal would violate minimum balance'
               ELSE
       *> Check if withdrawal exceeds daily limit
                   IF CURRENT-TRANSACTION-AMOUNT > CUSTOMER-DAILY-LIMIT
                       SET TRANSACTION-REJECTED TO TRUE
                       SET EXCEEDS-DAILY-LIMIT TO TRUE
                       DISPLAY 'ERROR: Withdrawal exceeds daily limit'
                   ELSE
                       SET TRANSACTION-APPROVED TO TRUE
                       DISPLAY 'Withdrawal validation passed'
                   END-IF
               END-IF
           END-IF.
       
       VALIDATE-DEPOSIT-REQUIREMENTS.
       *> Validate deposit-specific requirements (usually minimal)
       *> Most deposits are allowed unless they exceed system limits
           
           IF CURRENT-TRANSACTION-AMOUNT > 100000.00
               SET TRANSACTION-REJECTED TO TRUE
               SET NO-ERROR TO TRUE  *> Generic error for large deposits
               DISPLAY 'ERROR: Deposit amount exceeds system limit'
           ELSE
               SET TRANSACTION-APPROVED TO TRUE
               DISPLAY 'Deposit validation passed'
           END-IF.
       
       VALIDATE-TRANSFER-REQUIREMENTS.
       *> Validate transfer-specific requirements
       *> Transfers are treated as withdrawals from source account
           
           PERFORM VALIDATE-WITHDRAWAL-REQUIREMENTS
           DISPLAY 'Transfer validation completed'.
       
       EXECUTE-TRANSACTION-PROCESSING.
       *> Execute the actual transaction processing based on type
       *> This updates account balances and prepares audit information
           
           EVALUATE TRANSACTION-TYPE-CODE
               WHEN 'D'  *> Process deposit
                   ADD CURRENT-TRANSACTION-AMOUNT TO CUSTOMER-ACCOUNT-BALANCE
                   DISPLAY 'Deposit processed successfully'
               WHEN 'W'  *> Process withdrawal
                   SUBTRACT CURRENT-TRANSACTION-AMOUNT FROM CUSTOMER-ACCOUNT-BALANCE
                   DISPLAY 'Withdrawal processed successfully'
               WHEN 'T'  *> Process transfer (withdrawal from source)
                   SUBTRACT CURRENT-TRANSACTION-AMOUNT FROM CUSTOMER-ACCOUNT-BALANCE
                   DISPLAY 'Transfer processed successfully'
           END-EVALUATE.
       
       *> ================================================================
       *> AUDIT AND REPORTING PROCEDURES
       *> These procedures handle audit trail creation and result reporting
       *> ================================================================
       UPDATE-ACCOUNT-AND-AUDIT-TRAIL.
       *> Update the account record and create audit trail entries
       *> This ensures all transactions are properly logged for compliance
           
           IF TRANSACTION-APPROVED
               PERFORM UPDATE-CUSTOMER-ACCOUNT-RECORD
               PERFORM CREATE-AUDIT-TRAIL-ENTRY
               DISPLAY 'Account and audit trail updated successfully'
           ELSE
               PERFORM LOG-REJECTED-TRANSACTION
               DISPLAY 'Rejected transaction logged for audit'
           END-IF.
       
       UPDATE-CUSTOMER-ACCOUNT-RECORD.
       *> Update the customer account record with new balance
           DISPLAY 'Updating customer account record...'
           *> Account update logic would go here.
       
       CREATE-AUDIT-TRAIL-ENTRY.
       *> Create audit trail entry for approved transaction
           DISPLAY 'Creating audit trail entry...'
           *> Audit trail creation logic would go here.
       
       LOG-REJECTED-TRANSACTION.
       *> Log rejected transaction for audit and analysis
           DISPLAY 'Logging rejected transaction...'
           *> Rejection logging logic would go here.
       
       GENERATE-TRANSACTION-RESULTS.
       *> Generate final transaction results and error reports
           DISPLAY 'Generating transaction results...'
           DISPLAY 'Transaction Status: ' TRANSACTION-PROCESSING-STATUS
           DISPLAY 'Account Balance: ' CUSTOMER-ACCOUNT-BALANCE
           IF TRANSACTION-REJECTED
               DISPLAY 'Error Code: ' TRANSACTION-ERROR-CODE
           END-IF.

This example demonstrates excellent documentation practices with comprehensive comments that explain the business logic, data structures, and processing flow. The comments provide context for why certain validations are performed, what business rules are being implemented, and how the different procedures work together. This level of documentation makes the code much easier to understand and maintain.

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