Introduction to OOP

Chapter 27: Implementation :

Two General Approaches to Implementation

Compilers - translated into basic machine code, source code not available at run-time, generally very efficient.
Interpreters - translated into intermediate representation, source code available for reference at run-time, generally somewhat less efficient.

Endpoints are clear, but there are lots of gray areas in the middle.

Java JIT systems are one of those gray areas between compilers and interpreters