Writing reusable code is an important skill for any developer to have. It can significantly reduce the amount of time required to create a project and even improve the quality of the code. However, if we want to write maintainable and scalable software, we must learn how to write reusable code.

Definition of code reusability.

Code reusability is the ability of software components to be used more than once in the same or different applications. For example, let’s say we have written a routine which outputs some text on the screen. This routine can be used in many ways: as a standalone procedure which simply displays some static information. As the body of a subroutine which is called from another routine which performs some calculation and then calls the standalone routine to display the result. As a subroutine which is called by another routine which validates some data entered by the user and only when the data is valid, calls the standalone routine to output some confirmation information. Reusable code improves the quality of our applications because it reduces the amount of duplicate coding we need to do.

Ways to reuse code

The most important thing is to think about the software as a whole and not as a collection of individual procedures. For example, if you are developing an accounting application, think about the various accounts your application will have (Income, expense, etc.) not about the procedures which manipulate the data in those accounts. Also, think about how the various procedures interact with each other and not just about the procedure which manipulates the data.

There are no magic formulae to make our code more reusable. However, there are some simple guidelines to help us make our code more reusable. One of these guidelines is to make our code as independent as possible from the specific application in which we are using it. For example, if we have a routine which counts the number of vowels in a sentence, this routine does not belong to the accounting application. It should be a part of a general utilities’ library. Another guideline is to encapsulate our code in objects. For example, our Countdown object should encapsulate the counting algorithm and any other related information. Encapsulation makes our code more independent and easier to reuse because it removes all the intimate details about how the code works.

Think about how our code can be used by others. Can our code be used by another programmer who is not familiar with our application? If so, how could he or she use our code without having to understand our application? This will make our code more reusable and independent from our specific application.

Benefits of code reusability

Saves a lot of time

By reusing the existing code, you don’t have to write it all from scratch. This means less time is spent on writing the code and more time can be spent on refining and improving it.

Improves the quality of your product.

It also improves the quality of the product as a whole.This is because the existing code is tested and is used in the other software. This will allow developers to focus on the new features of the software. The existing code is tested by the other developers.

It enables you to create more features for your customers at less cost.

By writing reusable code, you will avoid having to rewrite a lot of it later. This means less work for you, less work for your customers, and less chance that something will go wrong. If you don’t write reusable code, you will be forced (time after time) to rewrite everything from scratch. This will cost you time, money and can even result in loss of your business.

Reusable code is also very likely to be more efficient than code which is not reusable. After all, if you have written something already three times, there’s a good chance you’ve got it “locked down.” You’ll know the rough shape of what the code should do, how it should behave, and the best way to structure it. If you write reusable code, the chances are excellent that you will end up writing something much more elegant, succinct and effective. Finally, when you write code which is not reusable, you are limiting your options.

For example, let’s say you are working on a new project, and you need to create an order entry system for selling products via the Internet. You have two basic options:

Write everything from scratch.

This means you will be starting from scratch with no built-in functionality. (This is the most time-consuming option.)

Reuse existing source code

Find and use some off-the-shelf software which already has everything you need (an Order Entry System) including a database, a shopping cart, a customer account system, a way to process credit card orders, etc.

The first option (writing everything from scratch) may seem like the faster option, but in reality it is the least efficient option. Why? Simply because it limits your options. If you do decide to write everything from scratch, you will almost certainly be forced to repeat a lot of effort. 

Types of code reuse

Opportunistic – As the team begins to get ready to start work on a new project, they realize there are existing components they can reuse.

Planned – Good designers are always thinking about how their work will be reused in future projects. They are not only good, but also they are strategic.

Reuse can be categorized further as internal and external reused.

Examples of code reuse in programming.

If a routine is used often, it should be put into a common code library, so it can be accessed easily by other programs. Common code libraries are usually part of an operating system or some other “core” software.

If you have a form that has a section asking for an address, and then another section asking for a description of the place, you can reuse the address information in the description section.

As another example, say you have a program that computes various statistics about your customers. You could write a separate program that just reads the first few lines of your description section and uses those as input to recompute the same statistics.

Code Reusability in Java.

In Java, you achieve code re-use by putting classes into a common package, and then you import that package into your other programs. Here’s an example: Imagine you have a class called Customer which has a field called address. Now imagine you have another class called Product which has a field called description. You could create a third class called Statistics, which has fields for the name of the customer, the address and the description. When you import the “Customer” package into your own program, you will do something like this: The “import” statement tells Java, “Hey, go get everything in the Customer package and put it into my project.” Now let’s say you want to compute the average price of your customers. To do that, you would create a fourth class called ‘AveragePrice’ which has fields for the name of the customer, the address and the average price. 

Code Reusability in C language 

In C language, Code reusability is achieved by using libraries and object-oriented programming. In C programming, a library is a set of related data types, functions, and other resources. These are logically grouped together in a single namespace to make the library more useful.

Code Reusability in Python

In Python, when you import a module, you are able to use the things defined in that module in your program. Into the same module, you can also include multiple classes / functions / methods / variables. These are known as the components of that module.

Python allows programmers to define new types at runtime. Python supports multiple programming paradigms, including object-oriented, imperative and functional programming or procedural styles. 


Code Reusability is the practice of writing reusable software components and then using these components in multiple projects rather than writing the components from scratch each time. The main advantages of code reuse are time savings, quality improvements, and cost reductions.

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