In computing, a compiler is a computer program that translates computer code written in one programming language (the source language) into another language (the target language). The name “compiler” is primarily used for programs that translate source code from a high-level programming language to a lower level language (e.g., assembly language, object code, or machine code) to create an executable program.
There are many different types of compilers which produce output in different useful forms. A compiler that can run on a computer whose CPU or operating system is different from the one on which the code it produces will run is called a cross-compiler. A bootstrap compiler is written in the language that it intends to compile. A program that translates from a low-level language to a higher level one is a decompiler. A program that translates between high-level languages is usually called a source-to-source compiler or transcompiler. A language rewriter is usually a program that translates the form of expressions without a change of language. The term compiler-compiler refers to tools used to create parsers that perform syntax analysis.