FALSE
In mainframe programming, `FALSE` represents the logical negative outcome of a condition or a binary state indicating "no," "off," or "not true." It is a fundamental concept in conditional logic and program flow control, guiding program execution based on whether a specific predicate is met.
Key Characteristics
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- Representation: Often represented by a specific value, such as
0(zero) in REXX, PL/I, and C,LOW-VALUESor a specific character (e.g.,'N') in COBOL, orX'00'(binary zero) in Assembler. - Conditional Evaluation: Used as the target state in
IF,EVALUATE,WHEN, andPERFORM ... UNTILstatements to direct program execution paths. - Logical Operations: Forms the basis of boolean algebra when combined with
TRUEusingAND,OR, andNOToperators to construct complex conditions. - Default State: Frequently serves as the initial or default state for flags and switches before a condition is met or an event occurs.
- Absence of Condition: Indicates that a specific condition or predicate has not been met, leading to an alternative processing path.
- Representation: Often represented by a specific value, such as
Use Cases
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- Error Handling: Initializing an
ERROR-FLAGtoFALSEand setting it toTRUEonly if an error condition is detected during data validation or processing. - Data Validation: Checking if a record is
VALID(e.g.,IF RECORD-VALID-FLAG IS FALSE THEN PERFORM 8000-ERROR-ROUTINE). - Loop Control: Terminating a
PERFORM ... UNTILloop when aCONTINUE-PROCESSING-FLAGbecomesFALSE, indicating no more data to process or a specific condition has been met. - Feature Toggling: Enabling or disabling specific program features or processing steps based on a configuration flag being
TRUEorFALSE.
- Error Handling: Initializing an
Related Concepts
FALSE is the logical complement of TRUE, and together they form the two possible states of a boolean variable or expression. It is central to conditional statements (IF, EVALUATE) and loop constructs (PERFORM ... UNTIL), dictating program flow. It is often stored in flags or switches, which are single-bit or single-character fields used to track binary states. In JCL, while not directly using TRUE/FALSE as values, the concept is mirrored in IF/THEN/ELSE constructs based on return codes, where RC=0 typically implies success (meaning the condition "no error" is true), and non-zero RCs imply an error (meaning the condition "error occurred" is true).
- Consistent Representation: Establish and adhere to a consistent representation for
TRUEandFALSEacross all modules and programs within an application (e.g.,0forFALSE,1forTRUEor'N'forFALSE,'Y'forTRUE). - Meaningful Names: Use descriptive variable names for boolean flags, such as
IS-RECORD-VALID, `HAS-