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Merge pull request #334 from oathar/lab2
Add Lab: Case Sensitive Nature of COBOL Conditions (Lab 9)
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‎COBOL Programming Course #2 - Learning COBOL/COBOL Programming Course #2 - Learning COBOL.md

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**Need Help?** If you encounter difficulties, you can refer to the complete solution code `CBLC1.cobol` available in VS Code Zowe Explorer or find it on [GitHub](https://github.com/openmainframeproject/cobol-programming-course/tree/master/COBOL%20Programming%20Course%20%232%20-%20Learning%20COBOL/Labs/cbl) repository.
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# Case Sensitive Nature of COBOL Conditions
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COBOL syntax is not case-sensitive for keywords and identifiers, but string literal comparisons in conditional expressions ARE case-sensitive. This distinction between language syntax and data comparisons can lead to programming errors that cause issues when your program interacts with:
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- **External input data**, such as text files or database records
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- **Conditional expressions** that depend on exact string matches
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- **Third-party systems** that expect a specific case format
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## Why It Matters
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The most dangerous aspect of case sensitivity errors is that they often go unnoticed during initial testing. Programs **compile successfully**, **run without errors**, but **produce incorrect results**. These kinds of "silent failures" can persist in production systems for long periods, potentially resulting in:
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- Inaccurate or misleading reports
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- Logic failures (e.g., skipping conditional branches)
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- Reports that appear complete but miss values
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- Data corruption or misrouting
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### Real-World Example
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Modern COBOL treats statements like:
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`MOVE MY-NUMBER TO YOUR-NUMBER`
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and
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`Move my-Number to your-Number` as **equivalent** because keywords and identifiers are case-insensitive.
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However, **COBOL conditions** are case-sensitive when checking **string values**:
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`IF USA-STATE = 'new York'` = Fails, mismatch due to case
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`IF USA-STATE = 'New York'` = Succeeds, case matches
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The comparison **fails silently** COBOL won't throw an error, but the result won't be as expected.
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## Lab
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**Case Sensitivity in Data Comparison:**
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Understand how case sensitivity in COBOL string comparisons can cause logical errors and learn to identify and fix these issues.
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**Scenario:** You'll investigate why a program designed to count "New York" clients returns zero when New York clients actually exist in the input data file (id.DATA).
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**Required Files:**
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- `CBL006A.cobol` - COBOL program source
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- `CBL006AJ.jcl` - JCL job to compile and execute
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- `id.DATA` - Input data file
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All files are available in your VS Code Zowe Explorer.
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### Instructions
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1. Open `CBL006A.cobol` from your VS Code Zowe Explorer.
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This program reads account records and counts how many clients are from `"New York"`.
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2. Submit the JCL job `CBL006AJ.jcl`. View the job output from the JOBS section.
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- Confirm that no syntax or runtime errors occurred.
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- Now carefully read the final line of the report. `New York Clients = 000`
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![](Images/image071.png)
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Ask yourself: *Is this the number of New York clients you expected?*
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3. Based on your understanding, where do you think the bug lies?
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- Consider the case format of both the **comparison string** and the **actual data** from the file (id.DATA).
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4. Go and update the source code `CBL006A.cobol` .
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- Modify the string literal in the IF condition to match the exact case format found in the data file
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5. Save your changes to `CBL006A.cobol`
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6. Recompile and resubmit the job `CBL006AJ.jcl`
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7. Verify that the report now correctly shows: `New York Clients = 005`
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![](Images/image072.png)
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\newpage
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# Arithmetic expressions

‎COBOL Programming Course #2 - Learning COBOL/Images/image071.png

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‎COBOL Programming Course #2 - Learning COBOL/Images/image072.png

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‎COBOL Programming Course #2 - Learning COBOL/Labs/cbl/CBL006A.cobol

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*-----------------------
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IDENTIFICATION DIVISION.
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*-----------------------
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PROGRAM-ID. CBL006A
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AUTHOR. Otto B. Boolean.
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*--------------------
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ENVIRONMENT DIVISION.
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*--------------------
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INPUT-OUTPUT SECTION.
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FILE-CONTROL.
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SELECT PRINT-LINE ASSIGN TO PRTLINE.
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SELECT ACCT-REC ASSIGN TO ACCTREC.
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*-------------
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DATA DIVISION.
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*-------------
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FILE SECTION.
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FD PRINT-LINE RECORDING MODE F.
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01 PRINT-REC.
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05 ACCT-NO-O PIC X(8).
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05 FILLER PIC X(02) VALUE SPACES.
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05 LAST-NAME-O PIC X(20).
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05 FILLER PIC X(02) VALUE SPACES.
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05 ACCT-LIMIT-O PIC $$,$$$,$$9.99.
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05 FILLER PIC X(02) VALUE SPACES.
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05 ACCT-BALANCE-O PIC $$,$$$,$$9.99.
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05 FILLER PIC X(02) VALUE SPACES.
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*
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FD ACCT-REC RECORDING MODE F.
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01 ACCT-FIELDS.
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05 ACCT-NO PIC X(8).
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05 ACCT-LIMIT PIC S9(7)V99 COMP-3.
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05 ACCT-BALANCE PIC S9(7)V99 COMP-3.
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05 LAST-NAME PIC X(20).
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05 FIRST-NAME PIC X(15).
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05 CLIENT-ADDR.
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10 STREET-ADDR PIC X(25).
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10 CITY-COUNTY PIC X(20).
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10 USA-STATE PIC X(15).
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05 RESERVED PIC X(7).
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05 COMMENTS PIC X(50).
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*
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WORKING-STORAGE SECTION.
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01 FLAGS.
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05 LASTREC PIC X VALUE SPACE.
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*
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* CHANGE 1: Modified variable structure to count New York clients
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* Original counted Virginia clients - now counts New York clients
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01 CLIENTS-PER-STATE.
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05 FILLER PIC X(19) VALUE
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'New York Clients = '.
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05 NEWYORK-CLIENTS PIC 9(3) VALUE ZERO.
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05 FILLER PIC X(59) VALUE SPACES.
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*
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01 HEADER-1.
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05 FILLER PIC X(20) VALUE 'Financial Report for'.
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05 FILLER PIC X(60) VALUE SPACES.
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*
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01 HEADER-2.
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05 FILLER PIC X(05) VALUE 'Year '.
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05 HDR-YR PIC 9(04).
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05 FILLER PIC X(02) VALUE SPACES.
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05 FILLER PIC X(06) VALUE 'Month '.
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05 HDR-MO PIC X(02).
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05 FILLER PIC X(02) VALUE SPACES.
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05 FILLER PIC X(04) VALUE 'Day '.
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05 HDR-DAY PIC X(02).
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05 FILLER PIC X(56) VALUE SPACES.
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*
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01 HEADER-3.
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05 FILLER PIC X(08) VALUE 'Account '.
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05 FILLER PIC X(02) VALUE SPACES.
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05 FILLER PIC X(10) VALUE 'Last Name '.
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05 FILLER PIC X(15) VALUE SPACES.
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05 FILLER PIC X(06) VALUE 'Limit '.
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05 FILLER PIC X(06) VALUE SPACES.
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05 FILLER PIC X(08) VALUE 'Balance '.
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05 FILLER PIC X(40) VALUE SPACES.
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*
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01 HEADER-4.
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05 FILLER PIC X(08) VALUE '--------'.
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05 FILLER PIC X(02) VALUE SPACES.
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05 FILLER PIC X(10) VALUE '----------'.
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05 FILLER PIC X(15) VALUE SPACES.
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05 FILLER PIC X(10) VALUE '----------'.
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05 FILLER PIC X(02) VALUE SPACES.
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05 FILLER PIC X(13) VALUE '-------------'.
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05 FILLER PIC X(40) VALUE SPACES.
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*
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01 WS-CURRENT-DATE-DATA.
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05 WS-CURRENT-DATE.
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10 WS-CURRENT-YEAR PIC 9(04).
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10 WS-CURRENT-MONTH PIC 9(02).
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10 WS-CURRENT-DAY PIC 9(02).
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05 WS-CURRENT-TIME.
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10 WS-CURRENT-HOUR PIC 9(02).
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10 WS-CURRENT-MINUTE PIC 9(02).
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10 WS-CURRENT-SECOND PIC 9(02).
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10 WS-CURRENT-CENTISECOND PIC 9(02).
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* This data layout is organized according to the ouput
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* format of the FUNCTION CURRENT-DATE.
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*
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*------------------
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PROCEDURE DIVISION.
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*------------------
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OPEN-FILES.
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OPEN INPUT ACCT-REC.
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OPEN OUTPUT PRINT-LINE.
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*
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WRITE-HEADERS.
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MOVE FUNCTION CURRENT-DATE TO WS-CURRENT-DATE-DATA.
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* The CURRENT-DATE function returns an alphanumeric value
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* that represents the calendar date and time of day
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* provided by the system on which the function is
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* evaluated.
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MOVE WS-CURRENT-YEAR TO HDR-YR.
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MOVE WS-CURRENT-MONTH TO HDR-MO.
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MOVE WS-CURRENT-DAY TO HDR-DAY.
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WRITE PRINT-REC FROM HEADER-1.
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WRITE PRINT-REC FROM HEADER-2.
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MOVE SPACES TO PRINT-REC.
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WRITE PRINT-REC AFTER ADVANCING 1 LINES.
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WRITE PRINT-REC FROM HEADER-3.
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WRITE PRINT-REC FROM HEADER-4.
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MOVE SPACES TO PRINT-REC.
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*
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READ-NEXT-RECORD.
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PERFORM READ-RECORD
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PERFORM UNTIL LASTREC = 'Y'
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* CHANGE 2: Updated paragraph name to reflect New York processing
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* Original was IS-STATE-VIRGINIA, now IS-STATE-NEWYORK
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PERFORM IS-STATE-NEWYORK
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PERFORM WRITE-RECORD
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PERFORM READ-RECORD
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END-PERFORM
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.
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*
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CLOSE-STOP.
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WRITE PRINT-REC FROM CLIENTS-PER-STATE.
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CLOSE ACCT-REC.
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CLOSE PRINT-LINE.
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GOBACK.
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*
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READ-RECORD.
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READ ACCT-REC
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AT END MOVE 'Y' TO LASTREC
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END-READ.
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*
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* CHANGE 3: Updated paragraph name and logic to check for New York
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* Original paragraph: IS-STATE-VIRGINIA
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* - Checked for 'Virginia' state
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* - Added to VIRGINIA-CLIENTS counter
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* Modified paragraph: IS-STATE-NEWYORK
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* - Now checks for 'New York' state
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* - Adds to NEWYORK-CLIENTS counter
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IS-STATE-NEWYORK.
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IF USA-STATE = 'new York' THEN
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ADD 1 TO NEWYORK-CLIENTS
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END-IF.
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* Boolean logic -- when the conditional expression
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* USA-STATE = 'New York' is true, the program
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* counts one more client from New York
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* Note -- the inclusion of the word THEN is optional
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* END-IF -- explicitly terminates the IF statement
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*
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WRITE-RECORD.
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MOVE ACCT-NO TO ACCT-NO-O.
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MOVE ACCT-LIMIT TO ACCT-LIMIT-O.
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MOVE ACCT-BALANCE TO ACCT-BALANCE-O.
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MOVE LAST-NAME TO LAST-NAME-O.
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WRITE PRINT-REC.
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*

‎COBOL Programming Course #2 - Learning COBOL/Labs/jcl/CBL006AJ.jcl

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//CBL006AJ JOB 1,NOTIFY=&SYSUID
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//***************************************************/
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//* Copyright Contributors to the COBOL Programming Course
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//* SPDX-License-Identifier: CC-BY-4.0
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//***************************************************/
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//COBRUN EXEC IGYWCL
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//COBOL.SYSIN DD DSN=&SYSUID..CBL(CBL006A),DISP=SHR
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//LKED.SYSLMOD DD DSN=&SYSUID..LOAD(CBL006A),DISP=SHR
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//***************************************************/
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// IF RC = 0 THEN
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//***************************************************/
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//RUN EXEC PGM=CBL006A
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//STEPLIB DD DSN=&SYSUID..LOAD,DISP=SHR
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//ACCTREC DD DSN=&SYSUID..DATA,DISP=SHR
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//PRTLINE DD SYSOUT=*,OUTLIM=15000
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//SYSOUT DD SYSOUT=*,OUTLIM=15000
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//CEEDUMP DD DUMMY
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//SYSUDUMP DD DUMMY
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//***************************************************/
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// ELSE
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// ENDIF

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