Title here
Summary here
Enums in COBOL
Our enum type ServerState has an underlying integer type. The possible values for ServerState are defined as constants.
IDENTIFICATION DIVISION.
PROGRAM-ID. EnumeratedTypesDemo.
DATA DIVISION.
WORKING-STORAGE SECTION.
* Define enum-like constants
77 ServerState PIC 9(02).
77 StateIdle VALUE 0.
77 StateConnected VALUE 1.
77 StateError VALUE 2.
77 StateRetrying VALUE 3.
* Define a table to store state names
01 StateNameTable.
05 StateNameOccurs OCCURS 4 TIMES.
10 StateNameValue PIC X(10).
PROCEDURE DIVISION.
* Initialize table with state names
PERFORM VARYING I FROM 1 BY 1 UNTIL I > 4
EVALUATE I
WHEN 1 MOVE "idle" TO StateNameValue (I)
WHEN 2 MOVE "connected" TO StateNameValue (I)
WHEN 3 MOVE "error" TO StateNameValue (I)
WHEN 4 MOVE "retrying" TO StateNameValue (I)
END-EVALUATE
END-PERFORM.
* Demonstrate state transitions
CALL 'TRANSITION' USING StateIdle
GIVING NewState.
DISPLAY "Transitioned to state: " StateNameValue (NewState + 1).
CALL 'TRANSITION' USING NewState
GIVING NewState2.
DISPLAY "Transitioned to state: " StateNameValue (NewState2 + 1).
STOP RUN.
* Transition procedure
TRANSITION SECTION.
TRANSITION-PARA.
EVALUATE TRUE
WHEN ServerState = StateIdle
MOVE StateConnected TO ServerState
WHEN ServerState = StateConnected
MOVE StateIdle TO ServerState
WHEN ServerState = StateRetrying
MOVE StateIdle TO ServerState
WHEN ServerState = StateError
MOVE StateError TO ServerState
WHEN OTHER
DISPLAY "Unknown state"
STOP RUN
END-EVALUATE.
EXIT PROGRAM.Define the appropriate transition mechanism:
TRANSITION PROCEDURE DIVISION USING State.
TRANSITION-PARA.
PERFORM EVALUATE TRANSITION-LOGIC State.
RETURNING ServerState.
TRANSITION-LOGIC PARA.
EVALUATE State
WHEN StateIdle
MOVE StateConnected TO ServerState
WHEN StateConnected
MOVE StateIdle TO ServerState
WHEN StateRetrying
MOVE StateIdle TO ServerState
WHEN StateError
MOVE StateError TO ServerState
WHEN OTHER
DISPLAY "Unknown state"
STOP RUN
END-EVALUATE.
EXIT.
```
Running the COBOL program involves compiling it and then executing the binary.
```sh
$ cobc -x -free enumerated_types_demo.cbl
$ ./enumerated_types_demo
Transitioned to state: connected
Transitioned to state: idleIn this example, we defined a state machine using COBOL, initialized the state name table, performed state transitions, and displayed the transitions. Now that we can run and build basic COBOL programs, let’s learn more about the language.