Hi Bill, Particularly since one of the selling points of Java is "write once run anywhere", there are no requirements to use a particular system. We will probably use OpenJDK by default when marking, but since we are using Java version 11 in this unit, any specification-compliant implementation of Java 11 should be fine. So either OpenJDK or Oracle's official JDK should be fine. Use whatever works better for you. I can foresee no reason we would require you to use a particular operating system for anything in this unit. If I am wrong and one of our assessments requires a particular system, we will make that clear in the specifications for that assessment. By default you may assume that you can use whatever you prefer. Cheers, Gozz