Freeing the essence of a computation

In theory, abstraction is important, but in practice, so is performance. Thus, there is a struggle between an abstract description of an algorithm and its efficient implementation. This struggle can be mediated by using an interpreter or a compiler. An interpreter takes a program that is a high level abstract description of an algorithm and applies it to some data. Don't think of an interpreter as slow. An interpreter is important enough to software that it is often implemented in hardware. A compiler takes the program and produces another program, perhaps in another language. The resulting program is applied to some data by another interpreter.