A newer idea in program preparation and portability is the concept of a virtual machine. For example, using the Java programming language, language statements are compiled into a generic form of machine language known as bytecode that can be run by a virtual machine, a kind of theoretical machine that approximates most computer operations. The bytecode can then be sent to any computer platform that has previously downloaded or built in the Java virtual machine. The virtual machine is aware of the specific instruction lengths and other particularities of the platform and ensures that the Java bytecode can run.