Question

Differentiate between library and the user defined function.

Short answer

Library functions are predefined; user-defined functions are custom-made by the programmer.

Step-by-step solution

Understanding Library Functions

Library functions are pre-written functions provided by programming languages or libraries. They are built into the language's standard libraries, and you can use them without writing the code from scratch. Examples include mathematical functions like square root and built-in functions like reading a file. To use a library function, you often need to import the corresponding library.

Learning About User-Defined Functions

User-defined functions are custom functions that you create to perform specific tasks. Unlike library functions, these are written by the programmer to address specific needs within a program. They allow for code reuse and better organization. You define these functions by specifying a name, parameters, and the code block that performs the function’s operation.

Comparing Library and User Defined Functions

Library functions are pre-packaged and ready to use, ensuring convenience and reliability based on standard implementation. On the other hand, user-defined functions provide flexibility and customization, allowing programmers to define specific functionality needed for their applications that is not available in standard libraries.

Conclusion of Differences

To summarize, the main difference is that library functions are pre-defined and provided by the language, usually for common tasks, while user-defined functions are written by the user for specific uses. Library functions offer standardization, while user-defined functions offer customization and flexibility.

Key concepts

Library Functions

In programming, library functions are like the pre-made tools you find in a toolbox. They are ready to use and save you time.
These functions are pre-written pieces of code provided by the programming language or a specific library.
For example, if you need to calculate a square root or manipulate a string, there are functions already available in most languages that do exactly that. Using library functions is straightforward. It generally requires you to import the library that contains the function, and then you can call it in your program.
Here's why they are beneficial:

• Time-Saving: You don't have to write common functions from scratch.
• Reliable: They are widely tested and reliable.
• Efficient: Built for performance by experienced developers.

If you find yourself needing a task that most developers usually use, look for a library function first.

User-Defined Functions

User-defined functions are akin to inventing your own tool when existing ones don't quite fit your needs.
These are custom functions that programmers write themselves for specific tasks that aren't covered by library functions or require special behavior. Creating a user-defined function allows you to give it a unique name and specify its parameters, which are the inputs it will take. You will also write out the operations it should perform.
This way, you can execute complex operations just by calling this function later in your code.

• Customization: Tailor the function to your program’s needs.
• Reusability: Write it once, use it wherever needed.
• Scalability: Modify easily as your needs change.

User-defined functions enhance your ability to manage complex programs by breaking them down into manageable pieces.

Programming Libraries

Programming libraries contain a set of tools (functions, classes, scripts) that you can use in your programs to avoid writing everything from scratch.
They are like a collection of tried and tested tools available directly out of the box, supporting developers with varied functionalities. Libraries can involve comprehensive modules such as graphic libraries, math libraries, or even data manipulation libraries.
Importing these libraries means you gain access to well-documented, standard sets of functions and tools to increase the efficiency of your coding.

• Variety: Libraries exist for nearly every programming need.
• Efficiency: Save effort and focus on unique features of your application.
• Community Support: Extensive documentation and community support
  to help understand and troubleshoot them.

Consider exploring existing libraries when looking to add features to a project, because they can enhance both speed and quality of development.

Custom Functions

Custom functions are a specialized type of user-defined function, tailored further to meet unique challenges.
These functions are crafted for very specific purposes that generally cannot be solved adequately with built-in functions or standard user-defined functions. Custom functions provide maximal flexibility by allowing the developer to dictate the precise variables and operations needed.
This specificity means you can create functions that perfectly match the requirements of your application, such as tailored data processing techniques or unique algorithms.

• Precision: Execute tasks down to exact specifications.
• Uniqueness: Solve complex problems where general functions fall short.
• Maintainability: Keep your codebase clean by isolating unique operations.

While more complex, custom functions shine when a high degree of customization is necessary.