A function is a set of statements that take inputs, do some specific computation, and produce output. The idea is to put some commonly or repeatedly done tasks together and make a function so that instead of writing the same code again and again for different inputs, we can call the function.

Why Do We Need Functions?

Functions help us in reducing code redundancy. If functionality is performed at multiple places in software, then rather than writing the same code, again and again, we create a function and call it everywhere. This also helps in maintenance as we have to change at one place if we make future changes to the functionality. Functions make code modular. Consider a big file having many lines of code. It becomes really simple to read and use the code if the code is divided into functions. Functions provide abstraction. For example, we can use library functions without worrying about their internal work.

Function Declaration

A function declaration tells the compiler about the number of parameters function takes data-types of parameters, and returns the type of function. Putting parameter names in the function declaration is optional in the function declaration, but it is necessary to put them in the definition. Below are an example of function declarations.