Function and Recursive

Function

So, program is divided into modules. The modules in C programming language are execute using function. Function is a group of sentence that does a specific job.

Function in C usually written above the int main()

The benefit of using Function :

1. A huge program can be divide into smaller modules.

2. Easier to fix if there is a problem.

3. Easier to document

Function Construction :

return_type_value function_name ( parameter-list )
{
   statement;
}

return-value-type :  data type of the value returned, 

• If not filled, then default data type will be used (integer)

• If return-value-type is void then the function will not return value

Parameter-list: list of value sent from the function initiator (user)

example : 
int maximum (int a,int b )
   {
     statement 
   }
int : return value type of integer
int a, int b : the parameter input by user
statement : all the task that function needs to do

Passing Parameter : If a module is not self sufficed then needed data/value and its result passes in and out using parameter(s)

Sending parameter can be by two ways :
   1. by value, is when you sent the value to the other module
   2. by location / reference, is by using array one dimension or two dimension

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Recursive

Is a function call, inside a certain function calling itself. And also recursive can be combined with function. 
Example : 
1. A recursive function to find a factorial n.
2. A recursive function to find a Fibonacci sequence 

When Making A Recursive, Recursive Function has two components :

- Base Case :  return value(constant) without calling next recursive call.
- Reduction step : sequence of input value converging to the base case.

Example: 
(Factorial function)
Base case : n = 0
Reduction step: f(n) = n * f(n-1)

The Bad Thing About using Recursive

- More memory consumption. 
- Takes longer time, should traverse through all recursive call using stack

Generally, use recursive solution if:

- Difficult to solve iteratively.
- Efficiency is less important in comparison with readability
- Memory efficiency and execution time are not the main concern. ( Consider carefully speed and efficiency using iterative approach, rather than nice logical design using recursive )