Java is both compiled and interpreted; the source code is compiled into bytecode, and the bytecode is
interpreted by the JVM. Further, many current implementations of the JVM offer just-in-time compilation
(JITC), which means that when the program first executes, the JVM actually compiles the bytecode into
machine instructions. Henceforth, executing the program runs a compiled program in object code form. The
goal of this design is to provide the advantages of both compilers and interpreters.
By the way, the term virtual machine in general describes an additional layer of abstraction between
the user and the hardware, and so computer scientists also use the term to describe software that makes one
type of computer appear to be another. For instance, the Digital Equipment Corporation VAX product line,
running the VMS operating system, was very popular in the 1980s and 1990s, and many programs were
written for that environment. Since those computers are no longer available, some people install virtual machines
(software) to make Linux (http://www.wherry.com/gadgets/retrocomputing/vax-simh.html) or Windows computers
(http://www.dynawell.com/charon-vax/) execute VAX programs and appear to be VAX/VMS computers.
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