What is modular programming ?

The concept of modular programming is inspired from modular design and basically is decomposing complex & large softwares into simples modules for an easy and faster implementation by allowing parallel developement of different parts of the system .

Modularity refers to the division of software into separate modules which are differently named and addressed and are integrated later on in order to obtain the completely functional software . it allows a program to be intellectually manageable , while single large programs are difficult to understand and read .

each module is a well defined system that can be used to with other applications
each module has a single specific purpose
modules can be separately compiled and stored in a library
modules can use other modules
modules should be easier to use than to build
modules are simpler from outside than inside

Modularity is all about making blocks, and each block is made with the help of other blocks. Every block in itself is solid and testable and can be stacked together to create an entire application. Therefore, thinking about the concept of modularity is also like building the whole architecture of the application.

Code is easier to read - Working on modular programming makes code easier to read because functions perform different tasks as compared to monolithic codes.

Code is easier to test - In software, some functions perform fewer tasks and also functions that perform numerous tasks. If the software is easily split using modules, it becomes easier to test.

Reusability - There are times where a piece of code is implemented everywhere in our program. Instead of copying and pasting it, again and again, modularity gives us the advantage of reusability so that we can pull our code from anywhere using interfaces or libraries. The concept of reusability also reduces the size of our program.

Faster fixes - Suppose there is an error in the payment options in any application, and the bug needs to be removed. Modularity can be a great help because we know that there will be a separate function that will contain the code of payments, and only that function will only be rectified. Thus using modules to find and fixing bugs becomes much more smooth and maintainable.

Easy collaboration - Different developers work on a single piece of code in the team. There are chances of conflicts when there's a git merge. This conflict can be reduced if the code is split between more functions, files, repos, etc. We can also provide ownership to specific code modules, where a team member can break them down into smaller tasks.

There is a need for extra time and budget for a product in modular programming
It is a challenging task to combine all the modules
Careful documentation is required so that other program modules are not affected
Some modules may partly repeat the task performed by other modules. Hence, Modular programs need more memory space and extra time for execution
It reduces the program's efficiency because testing and debugging are time-consuming, where each function contains a thousand lines of code

There is some concepts you should know about them like decoupling , coupling & cohesion :

Decoupling means that one module cannot depend on another module directly
Coupling is the act of joining two things together (modules)
Cohesion refers to the degree to which the elements inside a module belong together

The blog gonna end up just right here so you don't get bored and if you want to grasp more about that topic try to learn more about the last 3 concepts that we have just talked about briefly .