I may have over complicated my first post. I am using a class to run a test, and in this case I'm using it 3 times. Each class keeps track of how many cycles have been run of this test, but I would like to retrieve the data from each class and write it neatly into a file on an SD card. I have a working version that doesn't use classes, but as this is my first time using them, I'm having trouble. It doesn't even necessarily have to involve the SD card, if I know how to get the data together in one place even if it's just to Serial.print(); then I'll be well on my way.