Code as data

In computer science, the expressions code as data and data as code refer to the duality between code and data, that allows computers to treat instructions in a programming language as data handled by a running program.

Concepts where computer code is treated as data, or data executed as code, include:

• Configuration scripts, declarative programming, domain-specific languages and markup languages, where program execution is controlled by data elements that are not sequences of commands.
• First-class functions, functions that can be accessed as entities in the language.
• Homoiconicity, a property of languages like LISP where the code has the same structure as the data.
• Reflection and metaprogramming, the capability of a language to modify the structure and behavior of objects in the program at run time.
• Self-modifying code, the capability of a language to alter its own instructions while it is executing.
• Stored program, code in a computer with the Von Neumann architecture that stores programs and data in the same memory device.