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COBOL Tutorial

Working with Conditional Variables in COBOL

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88-Level Condition Names

One of COBOL's most distinctive and powerful features is the 88-level condition name. Condition names provide a way to create symbolic constants and assign meaningful names to specific values that a data item can have. This enhances code readability and maintainability by allowing programmers to use meaningful names instead of literal values in conditional expressions.

Basic 88-Level Condition Name Syntax

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       WORKING-STORAGE SECTION.
       01  WS-STATUS-CODE            PIC X.
           88  STATUS-ACTIVE         VALUE 'A'.
           88  STATUS-SUSPENDED      VALUE 'S'.
           88  STATUS-TERMINATED     VALUE 'T'.
           88  STATUS-PENDING        VALUE 'P'.

In this example, four condition names are associated with the WS-STATUS-CODE field, each representing a different status value.

The 88-level condition names are not separate data items but rather boolean conditions associated with the parent data item. When the parent item contains a value specified in the condition name's VALUE clause, the condition is considered true; otherwise, it's false.

Note: 88-level items don't occupy any additional storage. They simply provide a symbolic way to test whether their parent data item contains a specific value or one of a set of values.

Using Condition Names in Procedures

The primary benefit of 88-level condition names is that they can be used directly in conditional statements, making the code more readable and self-documenting. Instead of comparing a field to literal values, you can use descriptive condition names that clearly express the intent of the code.

Without Condition Names

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       IF WS-STATUS-CODE = 'A'
           PERFORM PROCESS-ACTIVE-ACCOUNT
       ELSE IF WS-STATUS-CODE = 'S'
           PERFORM PROCESS-SUSPENDED-ACCOUNT
       ELSE IF WS-STATUS-CODE = 'T'
           PERFORM PROCESS-TERMINATED-ACCOUNT
       END-IF.

With Condition Names

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       IF STATUS-ACTIVE
           PERFORM PROCESS-ACTIVE-ACCOUNT
       ELSE IF STATUS-SUSPENDED
           PERFORM PROCESS-SUSPENDED-ACCOUNT
       ELSE IF STATUS-TERMINATED
           PERFORM PROCESS-TERMINATED-ACCOUNT
       END-IF.

As you can see, using condition names makes the code much more readable and self-documenting. The intent is clear without needing to know the specific codes used for different statuses.

Using Condition Names in Other Contexts

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       * Using condition names in PERFORM UNTIL
       PERFORM PROCESS-RECORD
           UNTIL END-OF-FILE
 
       * Using the SET statement with condition names
       SET STATUS-ACTIVE TO TRUE
       
       * Using condition names with AND/OR
       IF VALID-CUSTOMER AND NOT ACCOUNT-CLOSED
           PERFORM PROCESS-TRANSACTION
       END-IF.

Condition names can be used in any context where a condition is expected, and they can be combined with AND, OR, and NOT operators.

Multiple Values for Conditions

An 88-level condition name can be associated with multiple values, either as individual literals or as ranges. This allows you to create conditions that represent a set of valid values, making your code even more expressive.

Multiple Individual Values

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       01  WS-DEPARTMENT-CODE         PIC X(3).
           88  SALES-DEPARTMENT       VALUE 'S01' 'S02' 'S03' 'S04'.
           88  MARKETING-DEPARTMENT   VALUE 'M01' 'M02' 'M03'.
           88  IT-DEPARTMENT          VALUE 'I01' 'I02' 'I03' 'I04' 'I05'.

In this example, SALES-DEPARTMENT is true if WS-DEPARTMENT-CODE contains any of the values 'S01', 'S02', 'S03', or 'S04'.

Value Ranges with THROUGH/THRU

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       01  WS-GRADE                   PIC 9(3).
           88  PASSING-GRADE          VALUE 60 THRU 100.
           88  FAILING-GRADE          VALUE 0 THRU 59.
           88  EXCELLENT-GRADE        VALUE 90 THRU 100.
           88  AVERAGE-GRADE          VALUE 70 THRU 89.
           88  POOR-GRADE             VALUE 60 THRU 69.

The THRU keyword (or THROUGH, they are synonymous) defines a range of values. In this example, PASSING-GRADE is true if WS-GRADE contains any value from 60 through 100, inclusive.

Mixing Individual Values and Ranges

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       01  WS-TRANSACTION-CODE        PIC X.
           88  VALID-TRANSACTION      VALUE 'A' 'B' 'C' 'D' THRU 'H' 'X' 'Y' 'Z'.
           88  PRIORITY-TRANSACTION   VALUE 'A' 'X' 'Y' 'Z'.
           88  STANDARD-TRANSACTION   VALUE 'B' 'C' 'D' THRU 'H'.

You can mix individual values and ranges in the same VALUE clause. Here, VALID-TRANSACTION is true for 'A', 'B', 'C', any letter from 'D' through 'H', and 'X', 'Y', 'Z'.

Best Practices for Condition Variables

To make the most effective use of 88-level condition names in your COBOL programs, follow these best practices:

Use Descriptive Names

Choose condition names that clearly describe what the condition represents, making your code self-documenting. Avoid abbreviations unless they are widely understood in your domain.

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       * Good - descriptive names
       88  CUSTOMER-IS-PREFERRED    VALUE 'P'.
       88  TRANSACTION-COMPLETED    VALUE 'C'.
       
       * Not as good - abbreviations, less clear
       88  CUST-PRF                 VALUE 'P'.
       88  TRANS-CMP                VALUE 'C'.

Group Related Conditions

Define all related condition names together right after their parent data item. This makes it easier to see all possible states that the data item can represent.

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       01  WS-ACCOUNT-STATUS          PIC X.
           88  ACCOUNT-ACTIVE         VALUE 'A'.
           88  ACCOUNT-DORMANT        VALUE 'D'.
           88  ACCOUNT-CLOSED         VALUE 'C'.
           88  ACCOUNT-FROZEN         VALUE 'F'.
           88  ACCOUNT-VALID          VALUE 'A' 'D'.  * Both active and dormant are valid

Define Complementary Conditions

When appropriate, define conditions that are logical complements of each other. This increases readability by avoiding negations in the code.

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       01  WS-VALIDATION-FLAG         PIC X.
           88  RECORD-IS-VALID        VALUE 'Y'.
           88  RECORD-IS-INVALID      VALUE 'N'.
           
       * Better to write:
       IF RECORD-IS-VALID
           PERFORM PROCESS-VALID-RECORD
       ELSE
           PERFORM PROCESS-INVALID-RECORD
       END-IF.
       
       * Instead of:
       IF NOT RECORD-IS-VALID
           PERFORM PROCESS-INVALID-RECORD
       ELSE
           PERFORM PROCESS-VALID-RECORD
       END-IF.

Use the SET Statement for Assignment

When setting a field to a value represented by a condition name, use the SET statement rather than moving literal values. This maintains consistency with your use of condition names.

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       * Preferred approach
       SET ACCOUNT-ACTIVE TO TRUE
       
       * Rather than
       MOVE 'A' TO WS-ACCOUNT-STATUS

Document Value Meanings

Even with descriptive condition names, it's good practice to include comments explaining what each value represents, especially for complex business rules or regulatory codes.

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       01  WS-TAX-CODE                PIC X(2).
           * Standard tax rates by region
           88  DOMESTIC-TAX            VALUE '01'.  * Standard domestic rate 20%
           88  EU-TAX                  VALUE '02'.  * European Union rate 15%
           88  INTERNATIONAL-TAX       VALUE '03'.  * International rate 25%
           * Special tax statuses
           88  TAX-EXEMPT              VALUE '00'.  * No tax charged
           88  REDUCED-RATE            VALUE '04'.  * Reduced rate for qualifying goods 5%

Alternative Approaches to Conditions

While 88-level condition names are a powerful COBOL feature, there are alternative approaches to representing conditions in your programs:

Using Symbolic Constants

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       01  STATUS-VALUES.
           05  STATUS-ACTIVE-VALUE    PIC X     VALUE 'A'.
           05  STATUS-INACTIVE-VALUE  PIC X     VALUE 'I'.
           05  STATUS-PENDING-VALUE   PIC X     VALUE 'P'.
       
       * Usage:
       IF WS-STATUS = STATUS-ACTIVE-VALUE
           PERFORM PROCESS-ACTIVE
       END-IF.

Using EVALUATE for Multiple Conditions

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       EVALUATE WS-STATUS
           WHEN 'A'
               PERFORM PROCESS-ACTIVE
           WHEN 'I'
               PERFORM PROCESS-INACTIVE
           WHEN 'P'
               PERFORM PROCESS-PENDING
           WHEN OTHER
               PERFORM PROCESS-UNKNOWN-STATUS
       END-EVALUATE.

Important: While these alternatives work, 88-level condition names generally provide the most readable and maintainable solution for representing symbolic conditions in COBOL programs. They're a core language feature specifically designed for this purpose.

Exercises

  1. Define and Use Status Conditions

    Create a WORKING-STORAGE data item for order status with condition names for "Pending", "Processing", "Shipped", "Delivered", and "Cancelled". Then write an IF/ELSE structure that performs different paragraphs based on the order status.

  2. Create Age Group Conditions

    Define a numeric field for a person's age, then create condition names for different age groups: "Child" (0-12), "Teen" (13-19), "Young-Adult" (20-39), "Middle-Age" (40-64), and "Senior" (65+). Write code that sets a discount percentage based on the age group.

  3. Convert IF/ELSE to Condition Names

    Refactor the following code to use 88-level condition names:
    IF WS-ACCOUNT-TYPE = 'S'
    PERFORM PROCESS-SAVINGS
    ELSE IF WS-ACCOUNT-TYPE = 'C'
    PERFORM PROCESS-CHECKING
    ELSE IF WS-ACCOUNT-TYPE = 'M'
    PERFORM PROCESS-MONEY-MARKET
    END-IF.

  4. Combine Conditions with AND/OR

    Define a customer record with fields for status (Active/Inactive) and type (Regular/Premium/VIP). Create condition names for each value, then write IF statements that combine these conditions to handle different scenarios (e.g., active premium customers).

  5. Use SET Statement with Conditions

    Write code that uses the SET statement to mark an order as "Shipped" and a customer account as "Active". Use appropriate condition names and document the expected effect on the underlying data items.

FAQ Section

Test Your Knowledge

1. What level number is used for condition names in COBOL?

  • 01
  • 66
  • 77
  • 88

2. What is the primary purpose of 88-level condition names?

  • To define tables
  • To create symbolic conditions for readability
  • To rename existing data items
  • To allocate memory

3. How many 88-level condition names can be associated with a single data item?

  • Only one
  • Up to five
  • Up to ten
  • As many as needed

4. How are 88-level condition names used in a COBOL program?

  • Like variables in arithmetic calculations
  • In IF statements as conditions
  • As destinations in MOVE statements
  • In PERFORM statements as loop counters

5. Which of the following is a valid use of an 88-level item?

  • 88 VALID-CODE PICTURE X.
  • 88 VALID-CODE VALUE "A" "B" "C".
  • 88 VALID-CODE USING WS-CODE.
  • 88 VALID-CODE COMPUTE WS-FLAG = "Y".

Related Concepts

COBOL Data Structures

Understanding how data is organized and structured in COBOL programs

Conditional Logic

Different ways to implement decision-making in COBOL

Program Flow Control

How to control the flow of execution in COBOL programs

Data Validation

Techniques for validating data in COBOL programs

Code Readability

Best practices for writing clear, maintainable COBOL code

OCCURS ClauseData Validation Techniques