// Function to add an exclamation mark to the end of a String
void appendExclamation(String &str) {
    str += "!"; // The original String is modified directly.
    Serial.print("inside 'appendExclamation': ");
    Serial.println(str);
}

void setup() {
    Serial.begin(115200);
    Serial.println("Hello, ESP32!");
    
    String myString = "Hello 5COM2004";
    Serial.print("Original string: ");
    Serial.println(myString); // Prints "Hello"

    appendExclamation(myString);

    Serial.print("After appendExclamation: ");
    Serial.println(myString); // Prints "Hello!"
}

void loop() {
    // Nothing to do here.
    delay(10000);
}