Channel Directions in COBOL

COBOL doesn’t have a direct equivalent to Go’s channels, so we’ll simulate the concept using file handling for inter-program communication. We’ll create two separate programs to represent the ping and pong functions, and use a temporary file to pass messages between them.

First, let’s create the PING program:

       IDENTIFICATION DIVISION.
       PROGRAM-ID. PING.
       ENVIRONMENT DIVISION.
       INPUT-OUTPUT SECTION.
       FILE-CONTROL.
           SELECT MESSAGE-FILE ASSIGN TO "message.tmp"
               ORGANIZATION IS LINE SEQUENTIAL.
       DATA DIVISION.
       FILE SECTION.
       FD MESSAGE-FILE.
       01 MESSAGE-RECORD PIC X(50).
       WORKING-STORAGE SECTION.
       01 WS-MESSAGE PIC X(50).
       PROCEDURE DIVISION.
       MAIN-PROCEDURE.
           OPEN OUTPUT MESSAGE-FILE.
           MOVE "passed message" TO WS-MESSAGE.
           WRITE MESSAGE-RECORD FROM WS-MESSAGE.
           CLOSE MESSAGE-FILE.
           STOP RUN.

This program writes a message to a file, simulating sending a message through a channel.

Now, let’s create the PONG program:

       IDENTIFICATION DIVISION.
       PROGRAM-ID. PONG.
       ENVIRONMENT DIVISION.
       INPUT-OUTPUT SECTION.
       FILE-CONTROL.
           SELECT MESSAGE-FILE ASSIGN TO "message.tmp"
               ORGANIZATION IS LINE SEQUENTIAL.
       DATA DIVISION.
       FILE SECTION.
       FD MESSAGE-FILE.
       01 MESSAGE-RECORD PIC X(50).
       WORKING-STORAGE SECTION.
       01 WS-MESSAGE PIC X(50).
       PROCEDURE DIVISION.
       MAIN-PROCEDURE.
           OPEN INPUT MESSAGE-FILE.
           READ MESSAGE-FILE INTO WS-MESSAGE
               AT END
                   DISPLAY "No message found"
               NOT AT END
                   DISPLAY WS-MESSAGE.
           CLOSE MESSAGE-FILE.
           STOP RUN.

This program reads the message from the file and displays it, simulating receiving a message from a channel and sending it to another.

To run these programs, you would compile them separately and then execute them in sequence:

$ cobc -x PING.cob
$ cobc -x PONG.cob
$ ./PING
$ ./PONG
passed message

In this COBOL implementation:

The PING program writes a message to a file, which simulates sending a message through a channel.
The PONG program reads the message from the file and displays it, which simulates receiving a message from one channel and sending it to another.

While this doesn’t capture the full concurrency aspect of Go’s channels, it demonstrates the concept of passing messages between programs in COBOL. For true concurrent operations in COBOL, you would need to use features specific to your COBOL implementation or operating system, such as multi-threading or sub-program calls, which are beyond the scope of this basic example.

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Channel Directions in COBOL