What is the difference between procedural and functional programming languages?

Procedural programming is about writing procedures or methods that perform operations on the data, while functional programming is about creating and applying mathematical functions.

Procedural programming is a programming paradigm that uses a linear or top-down approach. It is centred around the concept of procedure calls where different procedures are written to perform specific tasks. These procedures, also known as routines, subroutines or functions, are a series of computational steps to be carried out. The main focus of procedural programming is to break down a programming task into a collection of variables, data structures, and subroutines, whereas in a large procedural codebase, maintaining and updating code can be quite tricky. or a broader understanding, see Understanding Programming Paradigms.

On the other hand, functional programming is a programming paradigm where programs are constructed by applying and composing functions. It is a declarative type of programming style that emphasises on what to solve rather than how to solve (which is primarily focused in procedural programming). Its main focus is on 'what' you are doing and not 'how' you are doing it. Functional programming languages are designed on the concept of mathematical functions that use conditional expressions and recursion to perform computation. They avoid changing-state and mutable data. In functional programming, the output value of a function depends only on the arguments that are input to the function.

In procedural programming, data and functions are separate and distinct, whereas in functional programming, data and functions are somewhat combined. This means that in procedural programming, a list of instructions is used to tell the computer what to do step-by-step. In contrast, in functional programming, computations are treated as the evaluation of mathematical functions based on lambda calculus. To explore fundamental programming constructs used in these paradigms, you can visit Introduction to Fundamental Programming Constructs.

Additionally, understanding different programming paradigms can enhance your comprehension of how procedural and functional paradigms fit into the broader spectrum of programming. This contextual understanding can be deepened by exploring Features of OOP Core Principles, which discusses another major programming paradigm.

A-Level Computer Science Tutor Summary: Procedural programming involves writing step-by-step instructions to perform tasks, focusing on 'how' to solve problems. Functional programming, on the other hand, builds programs by using and combining functions, concentrating on 'what' to solve. While procedural code separates data and functions, functional programming integrates them, relying on mathematical functions and avoiding data changes.