Easytrieve Boolean Concepts

No Dedicated Boolean Type

DEFINE field-length table lists A, M, K, N, P, B, U, and I. None is boolean. You cannot declare ACTIVE-BOOL as type BOOL with values TRUE and FALSE. Instead, define ACTIVE-FLAG as A 1 and compare IF ACTIVE-FLAG EQ Y. Or use N 1 0 with zero meaning false and one meaning true in shop convention. The compiler evaluates conditions at runtime; storage is always another data type underneath.

IF Statement Structure

IF wraps conditional execution. When the condition is true, statements between IF and ELSE or END-IF run. Optional ELSE provides false branch. END-IF closes the block—nesting requires balanced END-IF for each IF. Missing END-IF is a frequent compile error in indented source editors that hide structure.

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IF SERVICE GT 14
   PERFORM BONUS-CALC
END-IF
 
IF SERVICE GT 19
   BONUS = 2000
ELSE
   BONUS = 1000
END-IF

Condition Categories

Relational Operators

Compare fields to literals or other fields with EQ equal, NE not equal, LT less than, GT greater than, LE less or equal, GE greater or equal. Spelling out EQ instead of equals sign is Easytrieve tradition—readable in column-oriented listings. Compare like types when possible: numeric to numeric, character to quoted literal. Mixing types may invoke conversion rules that surprise beginners—test boundary values in FLDCHK debug runs.

AND and OR Evaluation Order

Broadcom documentation states AND-connected conditions evaluate before OR groups. Within an AND chain, all must be true for the chain to succeed. Within OR, any true condition makes the OR group true. Parentheses in some expression contexts clarify intent—when in doubt, split complex logic into nested IF blocks or named PROCs for auditability. Operations teams reviewing payroll exceptions prefer readable nested IF over single line with four AND connectors.

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IF EMPL-NUM NUMERIC AND EMPL-NUM GT 15555
   PRINT EXCEPTION-RPT
END-IF
 
IF REGION EQ 'N' OR REGION EQ 'S' OR REGION EQ 'E'
   WS-ZONE = 'COASTAL'
END-IF

DO WHILE Loops

DO WHILE condition repeats a block while condition stays true—boolean logic identical to IF expression grammar. Increment counters inside the loop and ensure condition eventually becomes false to avoid infinite batch jobs consuming CPU until operators cancel. Combine with GOTO and END-DO per program style guides at your site.

Flag Fields as Pseudo-Booleans

Single-character flags are the closest storage analog to boolean. ACTIVE A 1 holds Y or N. ERROR-FLAG A 1 holds space or E. PROCESS-IND N 1 0 holds 0 or 1. Assignment sets flag; IF tests flag. Multiple flags sometimes pack into one binary B field with bit masks—each bit acts as independent boolean at the hardware level. Choose character flags when humans read dumps; choose bits when interfacing binary APIs.

Class Conditions

Class conditions test field content category without comparing to a specific value. NUMERIC asks whether characters are valid digits for numeric conversion. ALPHABETIC and related class tests appear in validation before arithmetic. Use class conditions as guards—IF ACCT NUMERIC AND ACCT GT 0 prevents S0C7 on alphabetic garbage in account fields.

THRU Range Conditions

IF SERVICE EQ 6 THRU 10 assigns vacation hours only when service years fall in band six through ten inclusive. THRU replaces multiple OR comparisons for contiguous numeric ranges. Boundaries are inclusive on both ends per training manual examples. Off-by-one errors happen when developers use LT and GT instead of THRU without aligning endpoints.

NOT and Negation

Negate conditions with NE not equal or by restructuring IF ELSE branches. Some extended condition forms support NOT connector in logical expressions per release documentation. When negation grows confusing, prefer positive IF with clear ELSE over double negatives that confuse maintainers during midnight incident response.

Boolean Logic vs Bit Logic

IF conditions are program-flow boolean. AND OR XOR on assignment with hex masks are bit-level boolean on bytes—different layer. IF STATUS-FLAG EQ Y is flow control. F1 = F2 AND X'FFFE' clears bit zero in a halfword. Both are boolean in computer science terms but serve different purposes. See bit fields and hex values pages for mask layer.

Common Boolean Mistakes

• Comparing Y flag to numeric 1 without conversion.
• Assuming uninitialized A flag is N—it may be space or LOW-VALUES.
• Complex AND OR without understanding evaluation order.
• Using GT on character fields expecting numeric sort order.
• Forgetting END-IF on nested IF blocks.

Explain It Like I'm Five

Boolean is asking yes-or-no questions. Is it raining? If yes, take an umbrella. Easytrieve does not have a special true-false coin in your pocket—it asks questions about boxes labeled with field names. Is the box labeled SERVICE bigger than ten? If yes, do the bonus steps. Y and N stickers on a one-letter box are the closest thing to a true-false coin you can store.

Exercises

1. Write IF with ELSE setting BONUS 2000 or 1000 based on SERVICE GT 19.
2. Combine two conditions with AND for numeric validation plus threshold.
3. Define Y/N flag and test with IF before PRINT.
4. Rewrite three OR region tests as one THRU if regions were numeric codes 1-3.
5. Explain difference between IF flag EQ Y and bit AND mask testing.