What is the advantage of c function?

Answer 1

You cannot write a C program without writing at least one function, the main function (the entry point of the application). While it is possible to write all code within this one function, a non-trivial program would be difficult to maintain. When we write code as a single function, we often find ourselves writing duplicate code. That is; code where one or more operations is performed in the same sequence but where the operands may differ in name or value. Such code blocks are best replaced with a single function call. The main reason for this is that code duplication is difficult to maintain. If we decide to alter the code, we're usually forced to replace the code in all the duplicates as well. By placing the code in a function, we only have to update the code in one place.

We can also use functions to reduce a complex function to a series of simple function calls. With well-named functions, the complex function becomes self-documenting, easier to read and therefore easier to maintain. This is no different to breaking a complex task down into a series of much simpler tasks and delegating those tasks to the people best suited to that task.

Given that readability is fundamental to ease of maintenance, most functions become very simple, often just a single statement or algorithm. We call these functions low-level functions. They may not do very much work by themselves, but they allow us to hide low-level implementation details that would otherwise be a distraction. This allows us to concentrate on the problem at a much higher level of abstraction, creating simple high-level functions that do nothing more than coordinate calls to the low-level functions. With a well-designed system, the main function's task is reduced to processing the command-line arguments, coordinating calls to high-level functions and handling any errors returned from those functions. Each of these tasks can also be delegated to a separate function thus simplifying the main function even further.