Why Programming Languages Can’t Exist Without Functions

Ben Stegner 26-02-2018

One of the most basic building blocks of programming 10 Basic Programming Principles Every Programmer Must Know Your code should be clear and easy to maintain. Here are several other programming principles to help you clean up your act. Read More are functions. You can write extremely simple programs without them, but everything beyond “Hello World” demos will likely need to utilize functions eventually.


Have you ever wondered why functions are a cornerstone of so many programming languages? Let’s look into the reasons why they’re so vital and what they do for programmers.

What Is a Function, Anyway?

Simply put, a function in programming is a named group of code that performs a specific task. Depending on the language, you may also hear them called subroutines or procedures.

Once you define a function, you put code in it just like you would anywhere else in the program. By giving the function a name and defining parameters it should accept, you can pass information to the function and return some result. Functions are re-usable, so once you write one, you can call it anywhere else in your program.

So functions are useful, but what purposes do they serve?

1. Functions Encapsulate Tasks

Introductory programming classes often describe functions as “black boxes.” That is, when a programmer calls a function, they don’t care what exactly the code inside it does; they just need the result.


For example, if you wrote a function to read in lots of numbers from a text file and calculate the mode, you wouldn’t need to know how it works to use it. As long as you knew that the function expects a text file filled with numbers as input and outputs a number as the result, you could use it in any program without much trouble.

2. Functions Separate Tasks

But this isn’t the only way that functions encapsulate code. They also allow programmers to cleanly divide their code into segments.

While your main function might only have a few dozen lines of code, it could call multiple functions and perform complex operations through them. This is the core of object-oriented programming Characteristics of C Programming That Make It Unique (And Better) The C programming language is the mother of all modern programming languages. Almost every language in use today includes several features which first appeared in the C language. Read More . Plus, it helps split up large programs into smaller pieces so multiple people can work on them.

3. Functions Let You Reuse Code

Chances are that when you write some code to perform a task, you’ll use it more than once in your program.


Copying and pasting the needed code into multiple places is a bad idea. Not only does it add more complexity to your program, but it introduces more places for something to go wrong 10 Most Common Programming and Coding Mistakes Coding mistakes can lead to so many problems. These tips will help you avoid programming mistakes and keep your code meaningful. Read More . If you change something in the original block, you have to remember to re-paste it everywhere else.

Functions eliminate this problem. They make it easy to reuse code anywhere else in your program. Once you’ve defined a function, you can call it anytime and be sure that it will run the same way. This saves time and reduces complexity, which are two welcome qualities for a program.

4. Functions Enable Easier Shareability

At many companies today, the functions one programmer writes may be used by others in the company in other projects.

Since functions stand on their own, they’re very portable. Reusing them where appropriate cuts down on duplicate work, makes more efficient use of programming resources, and helps with developing standards across a company.


5. Functions Make Testing and Debugging Easier

Most programmers know the pain of trying to debug spaghetti code: a tangled, confusing mess that’s nearly impossible to follow as it has little structure. Without clear functions, programs jump all over the place. This makes it hard to debug, and a massive pain for someone coming in fresh to understand.

With everything clearly divided into functions, programmers can use unit tests to confirm that these functions work as they should. Instead of having to sort through the entire program to pinpoint an issue, they can isolate it to one function.

Functions increase readability, as well. A clean set of code 10 Tips for Writing Cleaner & Better Code Writing clean code looks easier than it actually is, but the benefits are worth it. Here's how you can start writing cleaner code today. Read More goes a long way in making it easy to maintain and follow. One alternative is confusing GOTO statements, which are heavily discouraged in modern programming.

Consider the simple example from Wikipedia, first with GOTO statements and then with a structured style, to see how this makes a difference:

1 i=0
2 i+=1
3 PRINT i; "squared=";i*i
4 IF i>100 THEN GOTO 6
5 GOTO 2
6 PRINT "Program Completed."

1 FOR i=1 TO 100
2 PRINT i;"squared=";i*i
3 NEXT i
4 PRINT "Program Completed."

6. Functions Divide Data and Logic

We talked about abstraction above; it’s important to note that functions help you separate the steps from the actual data. As long as you pass the function parameters it’s expecting, it doesn’t care what the data is. Each run of that function creates temporary variables and then discards them after it returns a result. This keeps your namespace clear and lets you reuse short-term variable names like “x”.

Keeping your important data outside the functions helps prevent unwanted modification The 10 Worst Programming Mistakes in History In its storied past, coding wrought destruction as well. Instances of a little bit of bad code caused disaster on a major level. The following are 10 of the worst programming mistakes in history. Read More . This is a smart step in modern programming.

7. Built-In Functions Are Important Too

Typically when we discuss functions we’re talking about user-created functions, but they aren’t the only type of function. All programming languages include functions that you can use without having to create them yourself.

For instance, no matter which language you’re using, you don’t have to write functions for basic arithmetic, printing text to the screen, and similar tasks. Can you imagine what a waste of time it would be if you were required to tell the computer how to perform these basic operations?

Functions Are Vital for Programming

Now you know why programming languages use functions, and why they’re so important. The biggest reasons for including functions all come down to one truth: functions allow you to break a program into more manageable pieces. When you do this, your program becomes simpler to manage, easier to test, and apt for reuse.

Without functions, programs would have loads of duplicate code, wouldn’t flow in a logical order, and would have no separation of utility. That would be a nightmare for managing, testing, and debugging. Thank goodness programming languages use them!

For more programming basics, check out our explanation on how do-while loops work How Do-While Loops Work in Computer Programming Loops are one of the first control types you'll learn in programming. You probably know about while and for loops, but what does a do-while loop accomplish? Read More .

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  1. Jonathan Day
    February 26, 2018 at 9:25 pm

    I am horrified.

    Everyone with a degree in any field of computing knows the definitions of standard terms. Functions take in zero or more values and return exactly one value. Procedures take in one or more values and return zero or more values. They are not the same. Subroutines differ by language - obviously gosub takes no values at all.

    It is worth noting that gosub allows code reuse since return returns to the location of the gosub call.

    Macros also allow code reuse in the source, without needing any programming elements. These code blocks are inserted at point of call and therefore eliminate the need for pushing values to the stack, which is slow.

    It should be noted that not all languages use a stack. Occam has procedures and functions, but does not permit recursion. Code is reused, but in a very different way to that of a typical language.

    Does this matter? Yes. Computer jargon is designed to make things clear, not obscure the very points the constructs were intended to make. Clarity is important and the lack of it is the main reason so many are put off from CS when, in truth, programming is no more difficult than explaining to someone how to boil an egg. If you can do the latter, you've constructed a program. As a different Michael Jackson would point out, that's really all there is to it.

  2. Ben
    February 26, 2018 at 5:00 pm

    Technically not true that all programming languages use functions. Look at the assembly language or BASIC. I agree that functions help making code maintainable so long as they are used correctly.

  3. Doreen
    February 26, 2018 at 4:59 pm

    Clearly written by a student, not an expert. Mostly ballast with no information. Mostly over- generalized statements . Several incorrect assertions.


  4. Jason Filippou
    February 26, 2018 at 4:36 pm

    Functions are so indispensable that I we have necessary library functions like pthread_create that take function pointers as arguments.

  5. Brian
    February 26, 2018 at 4:32 pm

    In this article you demonstrate that programming languages can exist without functions.

    Please fix the article so that it is not self-contadictory, preferably by abandoning the obviously false premise.