A programming paradigm describes a general strategy for how to write software. Formally, a ‘paradigm’ in everyday English is:
A set of assumptions, concepts, values, and practices that constitutes a way of viewing reality for the community that shares them.
Below is a hierarchy of very popular, battle-tested programming paradigms, each with their own pros and cons. You can solve pretty much any software problem in any paradigm, really, but the solution will differ in terms of scalability, maintainability, difficulty, etc.
Note: there are more paradigms than shown here.
Programming languages often support multiple programming paradigms. For example, JavaScript supports both object-oriented programming and functional programming (and more).
Imperative
Programs are a set of precise instructions for the machine to perform that mutate program state.
- Procedural – programs are just a sequential collection of data and functions (procedures) acting on that data. C is a classic example of a procedural language.
- Object-oriented – programs are just objects interacting with each other. Objects are just a container that groups together some data and methods (functions).
Declarative
Programs should be written descriptively, meaning that your code should always express the ‘what’ rather than the ‘how’. SQL, for example, is a declarative language, since the statement SELECT * FROM Table expresses what you want, but the ‘how’ is delegated tot he SQL engine. Ultimately,
- Functional – programs are made by calling and composing functions.
Ultimately, languages that support a declarative paradigm are just abstractions over an imperative ‘backend’.