Channel Synchronization in COBOL

COBOL doesn’t have built-in support for concurrent programming or channels like Go does. However, we can simulate a similar behavior using COBOL’s CALL statement and CANCEL statement for program control. Here’s an equivalent example:

       IDENTIFICATION DIVISION.
       PROGRAM-ID. MAIN-PROGRAM.
       
       ENVIRONMENT DIVISION.
       
       DATA DIVISION.
       WORKING-STORAGE SECTION.
       01 WS-DONE             PIC X VALUE 'N'.
       
       PROCEDURE DIVISION.
       MAIN-PROCEDURE.
           DISPLAY "Starting worker..."
           CALL "WORKER-PROGRAM" USING WS-DONE
           PERFORM UNTIL WS-DONE = 'Y'
               CONTINUE
           END-PERFORM
           DISPLAY "Worker finished"
           STOP RUN.

       IDENTIFICATION DIVISION.
       PROGRAM-ID. WORKER-PROGRAM.
       
       ENVIRONMENT DIVISION.
       
       DATA DIVISION.
       LINKAGE SECTION.
       01 LS-DONE             PIC X.
       
       PROCEDURE DIVISION USING LS-DONE.
       WORKER-PROCEDURE.
           DISPLAY "working..." WITH NO ADVANCING
           CALL "C$SLEEP" USING 1
           DISPLAY "done"
           MOVE 'Y' TO LS-DONE
           EXIT PROGRAM.

This COBOL program simulates the channel synchronization concept. Here’s how it works:

1. The MAIN-PROGRAM is equivalent to the main function in the original example.

2. We define a WS-DONE variable to simulate the channel. It’s initialized to ‘N’ (not done).

3. The WORKER-PROGRAM is called, which is equivalent to starting a goroutine.

4. The main program then enters a loop, continuously checking if WS-DONE has been set to ‘Y’. This simulates waiting for a value on a channel.

5. The WORKER-PROGRAM displays “working…”, sleeps for 1 second (using the C$SLEEP system call, which may vary depending on your COBOL implementation), then displays “done”.

6. After completing its work, the WORKER-PROGRAM sets LS-DONE to ‘Y’, which is equivalent to sending a value on the channel.

7. Once WS-DONE is ‘Y’, the main program exits the loop and finishes.

To run this COBOL program:

$ cobc -x main-program.cob
$ ./main-program
Starting worker...
working...done
Worker finished

Note that COBOL doesn’t have true concurrency like Go’s goroutines. The WORKER-PROGRAM runs synchronously when called. However, this example demonstrates how you might structure a COBOL program to achieve a similar flow of control and communication between program units.

If you removed the PERFORM UNTIL loop from the main program, it would exit immediately without waiting for the worker to finish, similar to removing the <- done line in the Go example.

COBOL’s approach to program structure and control flow is quite different from Go’s, but this example shows how you can achieve similar patterns of execution and communication between program units.