Interpreter (computing)

In computing, an interpreter is software that directly executes encoded logic. Use of an interpreter contrasts the direct execution^[1] of CPU-native executable code that typically involves compiling source code to machine code. Input to an interpreter conforms to a programming language which may be a traditional, well-defined language (such as JavaScript), but could alternatively be a custom language or even a relatively trivial data encoding such as a control table.

Historically, programs were either compiled to machine code for native execution or interpreted. Over time, many hybrid approaches were developed. Early versions of Lisp and BASIC runtime environments parsed source code and performed its implied behavior directly. The runtime environments for Perl, Raku, Python, MATLAB, and Ruby translate source code into an intermediate format before executing to enhance runtime performance. The .NET and Java eco-systems use bytecode for an intermediate format, but in some cases the runtime environment translates the bytecode to machine code (via Just-in-time compilation) instead of interpreting the bytecode directly.

Although each programming language is usually associated with a particular runtime environment, a language can be used in different environments. For example interpreters have been constructed for languages traditionally associated with compilation, such as ALGOL, Fortran, COBOL, C and C++. Thus, the terms interpreted language and compiled language, although commonly used, have little meaning.