The "control unit" you are talking to is Processing. I don't understand this statement.
The control unit I am talking to is not "Processing". By Processing I meant the software from www.processing.org.
The control unit is fixed on a car. A variety of the sensors on the car send data to the control unit, which can do a variety of things to the data. One of the things that the control unit can do, is to send out serial data regarding the sensor readings from it's serial output. I am receiving these data using an Arduino Mega's Serial port 1 and sending it out using an Xbee module.
I have an Arduino Uno with another Xbee module on it, which receives the data and does things to it as you have seen in my code. I have also written a code using the Processing software that I mentioned previously, which allows me to display things nicely on my laptop. So the control unit on the car is currently sending data to the Mega at 19200 bps, and in it's manual, this is the recommended baud rate.
I showed you. One letter is sufficient to define each of the different types of data you are sending.
I see. So I will be better off writing the full text like "Air temp" inside my Processing code rather than prompting Uno to print it and then use Processing to show that.