Function and Recursion

A function is a grouping of statements that are created to do a particular job. Modules are required when a group of statements are frequently used by other distinct code. These are called Sub-Program.
Together, they referred to as Modular Programming.
Advantages:

• An easily comprehensible top-down design
• Can be done by more than one developers
• Easy to debug
• Modifications can be done without affecting the overall code
• Easier to document

Functions are divided into two types:

• Library function, a standard function provided by the code compiler
• User-defined function, a self defined function

In addition to Function, there are also Identifiers. There are two types:

• Local Identifier, which are declared in the function and are limited to the functions
• Global Identifier, which are declared outside the function, can be re-declared in the function, and can be reached from anywhere in the program

Do note, however, that it is advisable not to use Global Variable for a number of reasons:

• Error rates increase
• Difficult to debug
• Low Data Exclusivity

If a module is not self-sufficient then the data and its result use parameters to pass through. these passing parameters are the interface of modules to other modules.
They are divided into two types:

• By-Value Parameters, that send value to other modules
• By-Location Parameters, that send address to other modules

A recursive is a function call inside a certain function calling itself. They are made up of two components:

• Base Case, which is the return value
• Reduction Step, a series of input converging on the base case

Despite recursive code being rather concise, it needs:

• More memory consumption
• Takes longer time