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In computer science, an ''interpreter'' is a computer program that directly executes, i.e. ''performs'', instructions written in a programming or scripting language, without previously compiling them into a machine language program. An interpreter generally uses one of the following strategies for program execution: # parse the source code and perform its behavior directly. # translate source code into some efficient intermediate representation and immediately execute this. # explicitly execute stored precompiled code〔''In this sense, the CPU is also an interpreter, of machine instructions.''〕 made by a compiler which is part of the interpreter system. Early versions of Lisp programming language and Dartmouth BASIC would be examples of the first type. Perl, Python, MATLAB, and Ruby are examples of the second, while UCSD Pascal is an example of the third type. Source programs are compiled ahead of time and stored as machine independent code, which is then linked at run-time and executed by an interpreter and/or compiler (for JIT systems). Some systems, such as Smalltalk, contemporary versions of BASIC, Java and others may also combine two and three. While interpretation and compilation are the two main means by which programming languages are implemented, they are not mutually exclusive, as most interpreting systems also perform some translation work, just like compilers. The terms "interpreted language" or "compiled language" signify that the canonical implementation of that language is an interpreter or a compiler, respectively. A high level language is ideally an abstraction independent of particular implementations. == History== The first interpreted high-level language was Lisp. Lisp was first implemented in 1958 by Steve Russell on an IBM 704 computer. Russell had read John McCarthy's paper, and realized (to McCarthy's surprise) that the Lisp ''eval'' function could be implemented in machine code.〔According to what reported by Paul Graham in ''Hackers & Painters'', p. 185, McCarthy said: "Steve Russell said, look, why don't I program this ''eval''..., and I said to him, ho, ho, you're confusing theory with practice, this ''eval'' is intended for reading, not for computing. But he went ahead and did it. That is, he compiled the ''eval'' in my paper into IBM 704 machine code, fixing bug, and then advertised this as a Lisp interpreter, which it certainly was. So at that point Lisp had essentially the form that it has today..."〕 The result was a working Lisp interpreter which could be used to run Lisp programs, or more properly, "evaluate Lisp expressions". 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Interpreter (computing)」の詳細全文を読む スポンサード リンク
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