In computing, source code, or simply code or source, is a plain text computer program written in a programming language. A programmer writes the human readable source code to control the behavior of a computer.

Since a computer, at base, only understands machine code, source code must be translated before a computer can execute it. The translation process can be implemented three ways. Source code can be converted into machine code by a compiler or an assembler. The resulting executable is machine code ready for the computer. Alternatively, source code can be executed without conversion via an interpreter. An interpreter loads the source code into memory. It simultaneously translates and executes each statement. A method that combines compilation and interpretation is to first produce bytecode. Bytecode is an intermediate representation of source code that is quickly interpreted.