Functional programming was very popular for about 60 years but after a long time, it is a niche phenomenon. However, expert programmers like Google Still rely on the basic concepts of this policy. There are very few programmers who can explain this programming clearly.

Languages like Java or Python are currently considered more effective for programming. Also, new languages like Haskell are now considered fully functional. Simply say, functional programming is about linking the building of immutable variables. Besides, in object-oriented programming functions set are fixed. Generally, it could be a changeable or a new value could be attached. Functional Programming is very important for tasks like machine learning and data analysis naturally. But this does not mean that a programmer will do only functional programming without object-oriented programming. However, you can use one for the convenience of work according to basic principles.

Functional Programming: Now a day, Functional programming is a notable event than object-oriented programming. Functional programming is considered quite effective in several languages, including python. Functional programming is considered great for machine learning, parallel programming, and creating large databases. Developers have been coming up with this idea for the past few decades. It cannot be ignored due to the many aspects of object-oriented programming. Having certain codes make this programming easier and more users friendly.

Pure and Impure Functional Programming: Functional Programming gives an output without any side effects. From the principle of functional programming, it can be said that this programming is written with basic function. Also, this pure function is never variable only creates a new one as output. So, no matter how much input you give in this programming, you will only get one as output. On the contrary, the impure function depends on some global variable, so if you give some input to this function, a different output value can show if it is a different global variable. This impure function strengthens debugging and program coding. There are some simple rules for checking side effects that can easily differentiate between pure function an impure function. For example, each function must have some input or output, and declarations will be impure without any input or output if the function has any side effect.

Lambda Functions of Functional programming: Analysing the history of functional programming, many people point out the discovery of Lambda Function. Although Lambda functions have a role in functional programming, they cannot be considered as the root cause. Lambda functions are one kind of tool which is used to activate any program. However, this function can be used in object-oriented programming.

Functional Programming languages: Some languages are useful for functional programming. These are advance from other programming languages. Some of these notable languages are given below:

· Perl: Perl takes different greet to side effects than most of the programming languages. It has some magic argument, $_, which is one of the main features. Perl also has many features that help make the program smooth.

· Java: Java language is not perfect for writing functional code. When writing a program in Java, there is about half a static keyword. However, this language is not designed for effective programming like machine learning software or database management.

· Scala: The main point of Scala is to combine functional programming and object-oriented programming. Object-oriented programming code can be kept inside to eliminate the side effects of the functional program. It has a purely functional program as output.

· Python: Python is the best and most effective language for functional programming. It can encourage a program to give a good output. Each of its function has at least one input. Python's Zen is very clearer than implicit.

· Clojure: According to Clojure's developer, it is almost 80% functional programming language. All its values are unchanging from the beginning just like a program needs. The desired output is obtained by changing the value around the default value. It is suitable for functional programming.

· Haskell: There are very few fully functional languages, Haskell is one of them. It is a newly discovered language by developers. Learning is not an easy task like other languages but it is valuable in terms of investment. Usually, in the case of debugging your program, it is with a functional programming code.

Advantage of Functional Programming: Functional programming is a way of doing authentic programming with function code. Its main function is to keep the data flow constant while controlling the data flow through function. Functional programming is one such example involving mathematical functions. In calculation, this functions input and output are between in a series. The importance of functional programming in the field of programming is highlighted through the following benefits:

· Concise Code: When it comes to coding, its feature helps to use fewer lines, short sentences, and increase program value.

· Predictability: According to the pure function, if you give the same input, the same output will come.

· Modularity: It encourages arranging blocks of coding in the case of pure function and running according to program logic.

· Testability: It is very easy to test the code blocks and change program format for development purposes.

· Parallel computing: Since these programming codes differ from one another, it is very easy to do parallel computing between them.

· Scalability: It is very easy to separate small and big programs from a modular code block. It is available to update for maintenance or to connect something new.

Conclusion: Programmers can use functional language to transform a program into mathematical operations in such a way that it can express itself. It can avoid mutable data and changing state. In computer science, it is considered as a programming pattern that is close to mathematical thinking. Efficient programming allows being parallel and consistent at no cost. In case of security issues and performance, it is better to use functional programming, even though Clojure and Haskell's programs have improved. Functional programming has many advantages and highly customized features, so it is much easier and more advance than another programming.