Psyco
CommonLanguageRuntime
ReadEvalPrint
Many modern
ProgrammingLanguages do not directly compile to machine-code but use an intermediary form, sometimes called bytecode (e.g. in the
Java-environment). This bytecode is then interpreted (or run on a
VirtualMachine) on the target-system. A
JIT translates the bytecode into machine-code on the fly and therefore optimizes execution (e.g. a JIT can take advantage of information over the current system at run-time).
A
VirtualMachine or an interpreter reads the bytecode and executes the machine-code the bytecode is a shortcut for. A JIT compiles the bytecode into machine-code, so reading the bytecode is done once. Further executions of that code directly use the machine-code generated in the first pass.