Functional programming is a coding strategy that focuses on the direct use of functions as first-class objects. This means that in a functional program, you are allowed to create, store, and call functions, and otherwise use them as if they were just another variable of the system. Functional code also simplifies programming decisions because it avoids changing state and mutable data. This type of functional manipulation allows programs to more closely express the desired behavior of the system and is particularly suitable to some application areas. Functional programming is especially useful in the development of mathematical software and in the processing of large datasets, as is the case in the analysis options and derivatives. It also can be used with the development of multi-threaded systems, since it allows the use of lock-free code.