Code reuse in the context of Cut, copy, and paste

Domain engineering is the entire process of reusing domain knowledge in the production of new software systems. It is a key concept in systematic software reuse and product line engineering. A key idea in systematic software reuse is the domain. Most organizations work in only a few domains. They repeatedly build similar systems within a given domain with variations to meet different customer needs. Rather than building each new system variant from scratch, significant savings may be achieved by reusing portions of previous systems in the domain to build new ones.

The process of identifying domains, bounding them, and discovering commonalities and variabilities among the systems in the domain is called domain analysis. This information is captured in models that are used in the domain implementation phase to create artifacts such as reusable components, a domain-specific language, or application generators that can be used to build new systems in the domain.

In computer programming, a macro (short for "macro instruction"; from Greek μακρο- 'long, large') is a rule or pattern that specifies how a certain input should be mapped to a replacement output. Applying a macro to an input is known as macro expansion.

The input and output may be a sequence of lexical tokens or characters, or a syntax tree. Character macros are supported in software applications to make it easy to invoke common command sequences. Token and tree macros are supported in some programming languages to enable code reuse or to extend the language, sometimes for domain-specific languages.

In computer programming, reusability describes the quality of a software asset that affects its ability to be used in a software system for which it was not specifically designed. An asset that is easy to reuse and provides utility is considered to have high reusability. A related concept, leverage involves modifying an existing asset to meet system requirements.

The ability to reuse can be viewed as the ability to build larger things from smaller parts, and to identify commonality among the parts. Reusability is often a required characteristic of platform software. Reusability brings several aspects to software development that do not need to be considered when reusability is not required.