Control Structures

// Simple IF statement
IF Temperature > 80.0 THEN
    CoolingFan := TRUE;
    OverheatAlarm := TRUE;
END_IF;

// IF-ELSE statement
IF StartButton THEN
    MotorRunning := TRUE;
ELSE
    MotorRunning := FALSE;
END_IF;

// IF-ELSIF-ELSE statement
IF Temperature > 90.0 THEN
    EmergencyShutdown := TRUE;
    AlarmLevel := 3;
ELSIF Temperature > 75.0 THEN
    CoolingFan := TRUE;
    AlarmLevel := 1;
ELSE
    CoolingFan := FALSE;
    AlarmLevel := 0;
END_IF;

CASE ErrorCode OF
    0:      // No error
        ErrorMessage := 'System OK';
        AlarmActive := FALSE;
        
    1..10:  // Minor errors
        ErrorMessage := 'Minor fault';
        AlarmActive := TRUE;
        AutoRestart := TRUE;
        
    11..50: // Major errors
        ErrorMessage := 'Major fault';
        AlarmActive := TRUE;
        AutoRestart := FALSE;
        
ELSE
    ErrorMessage := 'Unknown error';
    AlarmActive := TRUE;
END_CASE;

VAR
    I : INT;
    SensorValues : ARRAY[1..10] OF REAL;
    Sum : REAL := 0.0;
END_VAR

// Basic FOR loop
FOR I := 1 TO 10 DO
    Sum := Sum + SensorValues[I];
END_FOR;

// FOR loop with step
FOR I := 1 TO 10 BY 2 DO  // Steps: 1, 3, 5, 7, 9
    ProcessSensor(SensorValues[I]);
END_FOR;

// Countdown loop
FOR I := 10 TO 1 BY -1 DO
    ShutdownSequence[I] := TRUE;
END_FOR;

VAR
    Position : REAL;
    Target : REAL := 100.0;
    Speed : REAL := 5.0;
END_VAR

// WHILE loop - condition checked before execution
WHILE Position < Target DO
    Position := Position + Speed;
    MoveMotor(Speed);
    
    // Safety check
    IF Position > 120.0 THEN
        EXIT;  // Exit loop immediately
    END_IF;
END_WHILE;

// Process items until queue empty
WHILE NOT QueueEmpty DO
    Item := GetNextItem();
    ProcessItem(Item);
END_WHILE;

VAR
    Position : REAL;
    Attempts : INT := 0;
    MaxAttempts : INT := 5;
END_VAR

// REPEAT loop - condition checked after execution
REPEAT
    Position := ReadPosition();
    Attempts := Attempts + 1;
    
    IF Attempts > MaxAttempts THEN
        EXIT;  // Safety exit
    END_IF;
    
UNTIL Position > Target END_REPEAT;

// Retry logic
REPEAT
    Success := TryOperation();
    RetryCount := RetryCount + 1;
UNTIL Success OR (RetryCount >= 3) END_REPEAT;

// EXIT - immediately exit the loop
FOR I := 1 TO 100 DO
    IF ErrorCondition THEN
        EXIT;  // Jump out of loop
    END_IF;
    ProcessStep(I);
END_FOR;

// CONTINUE - skip to next iteration
FOR I := 1 TO 10 DO
    IF SensorValues[I] < 0 THEN
        CONTINUE;  // Skip negative values
    END_IF;
    ValidSum := ValidSum + SensorValues[I];
END_FOR;

// RETURN - exit function/program
IF CriticalError THEN
    RETURN;  // Exit immediately
END_IF;