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COBOL Tutorial

COBOL WAIT - Quick Reference

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Overview

WAIT is a modern COBOL statement that allows programs to pause execution for a specified time period or until a specific event occurs. It provides timing control and synchronization capabilities for coordinating program execution with external events or other processes.

Key Features

  • Time-based waiting - Pause execution for specified time periods
  • Event-based waiting - Wait for specific events to occur
  • Program synchronization - Coordinate with external processes
  • Timing control - Manage program execution timing

Syntax and Usage

WAIT statement syntax and usage patterns for different timing and synchronization scenarios.

Basic Time-Based WAIT

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       IDENTIFICATION DIVISION.
       PROGRAM-ID. WAIT-EXAMPLE.
       DATA DIVISION.
       WORKING-STORAGE SECTION.
       01  WAIT-TIME     PIC 9(3) VALUE 5.
       
       PROCEDURE DIVISION.
           DISPLAY "Starting program..."
           WAIT WAIT-TIME SECONDS
           DISPLAY "Waited for " WAIT-TIME " seconds"
           STOP RUN.

Basic WAIT statement that pauses execution for a specified number of seconds.

WAIT with Event Condition

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       IDENTIFICATION DIVISION.
       PROGRAM-ID. WAIT-EVENT.
       DATA DIVISION.
       WORKING-STORAGE SECTION.
       01  EVENT-FLAG    PIC X VALUE "N".
       01  MAX-WAIT-TIME PIC 9(3) VALUE 30.
       
       PROCEDURE DIVISION.
           DISPLAY "Waiting for event..."
           WAIT UNTIL EVENT-FLAG = "Y" OR MAX-WAIT-TIME SECONDS
           
           IF EVENT-FLAG = "Y"
               DISPLAY "Event occurred"
           ELSE
               DISPLAY "Timeout reached"
           END-IF
           
           STOP RUN.

WAIT statement that waits for an event or times out after a maximum period.

WAIT with Exception Handling

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       IDENTIFICATION DIVISION.
       PROGRAM-ID. WAIT-EXCEPTION.
       DATA DIVISION.
       WORKING-STORAGE SECTION.
       01  WAIT-DURATION PIC 9(3) VALUE 10.
       
       PROCEDURE DIVISION.
       MAIN-LOGIC.
           DISPLAY "Starting timed operation..."
           
           WAIT WAIT-DURATION SECONDS
           ON EXCEPTION
               DISPLAY "WAIT operation was interrupted"
               PERFORM HANDLE-INTERRUPTION
           NOT ON EXCEPTION
               DISPLAY "WAIT completed successfully"
           END-WAIT
           
           STOP RUN.
       
       HANDLE-INTERRUPTION.
           DISPLAY "Handling interruption..."
           EXIT.

WAIT statement with exception handling for interrupted operations.

Wait Types

Time-Based Wait

Wait for a specified time period.

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WAIT time-value SECONDS

Event-Based Wait

Wait until a condition becomes true.

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WAIT UNTIL condition

Combined Wait

Wait for event with timeout.

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WAIT UNTIL condition OR timeout SECONDS

Exception Handling

Handle WAIT interruptions.

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WAIT time-value SECONDS
ON EXCEPTION
    * Handle interruption

Best Practices

  • Use appropriate timeouts - Set reasonable timeout values for event-based waits
  • Handle exceptions - Always provide exception handling for WAIT operations
  • Consider performance - Avoid excessive waiting that may impact system performance
  • Document wait conditions - Clearly document what events or conditions the program is waiting for
  • Test thoroughly - Test WAIT operations with various timing scenarios

WAIT Quick Reference

Wait TypeSyntaxUse Case
Time DelayWAIT time SECONDSSimple timing delays
Event WaitWAIT UNTIL conditionWait for specific events
Timeout WaitWAIT UNTIL condition OR timeoutEvent wait with timeout
Exception HandlingWAIT time ON EXCEPTIONHandle interruptions

Test Your Knowledge

1. What is the primary purpose of WAIT in COBOL?

  • To terminate program execution
  • To pause program execution for a specified time or until an event occurs
  • To perform file operations
  • To handle exceptions

2. Which COBOL standard introduced the WAIT statement?

  • COBOL-68
  • COBOL-74
  • COBOL-85
  • COBOL 2002/2014

3. What types of WAIT operations are available?

  • Only time-based waiting
  • Only event-based waiting
  • Both time-based and event-based waiting
  • Only file-based waiting

4. How do you specify a time delay with WAIT?

  • WAIT FOR time-value
  • WAIT time-value SECONDS
  • WAIT UNTIL time-value
  • All of the above depending on implementation

5. What is a common use case for WAIT?

  • Program synchronization and timing control
  • File sorting operations
  • Mathematical calculations
  • Database connectivity

Frequently Asked Questions

Related Concepts

Program Control

Program flow and control structures.

Exception Handling

Handle program exceptions and errors.

Timing Control

Program timing and performance.

Synchronization

Program synchronization techniques.

Real-time Processing

Real-time program execution.

VARYINGWORKING-STORAGE SECTION