Byte-code is the set of instructions for Java Virtual Machine. Byte code is cross-platform, but any particular JVM is designed for appropriate OS, and this JVM only knows how to execute this byte-code under OS.
SCJP 6.0(95%), SCWCD 5(94%), SCJD (working on B&S v.2.3.1)
With a little knowledge, a cast iron skillet is non-stick and lasts a lifetime.