Difference Between Arguments and Parameters


While I was playing with the functions, I was wondering what is the difference between arguments and parameters. You might also have the same doubt, right? I thought both are the same. But they are not.

Sometimes you will hear the two terms used interchangeably and most people will know what you mean, but there are some actual differences.

So, I have done some research and I thought I should share this with you. By the end of this article, you will have a clear idea about both of these programming terms.

If you have come for a quick answer, here is the main difference between arguments and parameters.

A parameter is a variable in a method definition or function definition. They are also called formal parameters. When we call a method, arguments are the real data that we pass into the parameters of the method. They are also known as actual parameters. 

At the end of this article, I will tell you one cool trick to help you distinguish easily between arguments and parameters. Now, let’s understand these terms in detail with the help of examples.

An Example of Arguments and Parameters

Here is a simple Python program to show you the differences between arguments and parameters. This program has a method or function that takes two numbers as input and outputs the sum of those numbers.

def addNumbers(para1, para2):
    sum = para1 + para2
    print("The sum is " ,sum)

addNumbers(2,5)

This program will produce an output value “7”.

Take a look at this simple Python program to add two numbers. We have a function called addNumbers which contains two values inside the parenthesis, para1, and para2. These two values are called parameters.

I named it para1 and para2 so that you can understand quickly. These are two local variables, having a lifetime only inside the function. They can take any values that are passed when we call the method. So, these are the parameters.

Now, let’s look at the function call in this program. We called the function addNumbers at the last line of the program. Note that we have passed two values along with the function. These values are called arguments.

These are the real values that we give as input to get the desired output. They can have any values. For example, instead of (2,5), we can also pass say (3,4) which will give the output 7. So, all these values are called arguments of a function.

At the runtime of the program, parameters will take on the values of the arguments that are passed in. So, in our example Python program, the variable para1 will get the value of 2 and the variable para2 will get the value of 7.

Now, inside the program, there is a step that calculates the sum, by adding para1 and para2. So, in this scenario, 2 and 5 gets added and produce the sum 7. This is printed as the output of the program.

Is it okay to use ‘Arguments’ and ‘Parameters’ Interchangeably?

The consensus seems to be that it is okay to use these terms interchangeably in a team environment. Except perhaps when you are defining the precise terminology. In that case, you can also use formal argument/parameter and actual argument/parameter to disambiguate, which can be a pain to express sometimes.

I urge you to use both these terms correctly whenever they are necessary, even if you are not in a formal environment. It is better to be correct, right? So just try to use these terms suitably.

A simple trick to distinguish between Arguments and Parameters

Although parameters are also commonly referred to as arguments, arguments are more properly thought of as the actual values which are passed by the function calling or references assigned to the parameter variables when the subroutine is called at runtime.

Parameters work like placeholders. This placeholder belongs to the function naming and is used in the function body.

Here is a simple trick for you to remember the difference between arguments and parameters. Arguments are actual values. So we can connect both these words with the starting letter, A for arguments and A for actual values.  Also, parameters are placeholders. So, P for parameters and P for placeholders.

You can remember it using this trick. With this simple trick, you can exactly distinguish the terms whenever you hear them for the next time. If you are not satisfied with my trick, then you can create some other ideas to remember easily.

If you want another weird idea to distinguish between these terms, then take this. Think of the argument as the male part, and the parameter as the female part. The argument always goes into the parameter.

Do you have any other weird ideas? Let me know in the comments section down below.

A Real-World Example

A parameter is a very general or broad thing, but an argument is a very specific, concrete thing. Here is one real-world scenario for you.

Consider the case of a car. They accept petrol (unleaded gasoline) as an input. We can say that these machines accept parameters of type: petrol. The argument would be the exact and concrete input I put into my car. For example, the argument could be 30 liters of petrol/gasoline.

Let’s consider one more example. Parameters are the sockets of the plug-point which may take various different shapes. But only certain types of plugs fit them. These shapes are called data types. Parameters can be of different data types like int, char, array, object, etc.

Arguments will be the actual plugs that would be plugged into the plug points to activate certain equipment. So, the data types of arguments should be matching with the data types of the parameters. 

Important Points to Remember

Some programming languages allow for a default to be provided in the declaration of the function. In this case, if the caller omits the arguments, then the function will consider the default arguments.

A parameter has a calling mechanism along with a name and a datatype. There are mainly two calling mechanisms, which are call by reference and call by value.

In the call by value method, values of arguments are copied to the function’s parameters and these parameters are stored in different memory locations. So any changes made inside functions are not reflected in the arguments of the caller.

An argument does not have any name, but it can be a variable, a literal, or a constant value.

But, in the call-by-reference method, both the arguments and parameters refer to the same locations. Hence, any changes made inside the function are reflected in the arguments of the caller.

Make sure that the number of arguments in the function call and their data types match with the parameters of the function definition.

I hope you got a clear understanding of arguments and parameters in programming. You will be able to distinguish between these terms the next time when you use them.

If you still have any doubts or queries, let me know in the comments section down below. I will be happy to help you.

If you are ready to get started in programming, I recommend you to check out my article on the Basics of Python

If this article was helpful, do share it so that it will help more programmers like you.

Ashwin Joy

I'm the face behind Pythonista Planet. I learned my first programming language back in 2015. Ever since then, I've been learning programming and immersing myself in technology. On this site, I share everything that I've learned about computer programming.

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