Recursion (Recursive Function) :

Recursion (Recursive Function) :

When a function of body calls the same function then it is called as 'recursive function.'

Example:

Recursion()

{

        printf("Recursion !");

        Recursion();

}

Program :

#include <stdio.h>

#include <conio.h>

Recursion()

{

        int no;

        printf("\nRecursion... ");

        printf("\n\n Enter Number : ");

        scanf("%d",&no);

        if (no==3)

               exit(0);

        else

               Recursion();

}

void main()

{

        clrscr();

        Recursion();

}

Output :

Recursion...

 Enter Number : 2

Recursion...

 Enter Number : 1

Recursion...

 Enter Number : 3_

Features :

·         There should be at least one if statement used to terminate recursion.

·         It does not contain any looping statements.

Advantages :

·         It is easy to use.

·         It represents compact programming strctures.

Disadvantages :

·         It is slower than that of looping statements because each time function is called.

Note :

·         It can be applied to calculate factorial of a number, fibonancci series.

Functions in C :

Functions in C :

The function is a self contained block of statements which performs a coherent task of a same kind.

C program does not execute the functions directly. It is required to invoke or call that functions. When a function is called in a program then program control goes to the function body. Then, it executes the statements which are involved in a function body. Therefore, it is possible to call fuction whenever we want to process that functions statements.

Types of functions :

There are 2(two) types of functions as:

1. Built in Functions
2. User Defined Functions

1. Built in Functions :

These functions are also called as 'library functions'. These functions are provided by system. These functions are stored in library files. e.g.

·         scanf()

·         printf()

·         strcpy

·         strlwr

·         strcmp

·         strlen

·         strcat

2. User Defined Functions :

The functions which are created by user for program are known as 'User defined functions'.

Syntax:

void main()

{

        // Function prototype

        <return_type><function_name>([<argu_list>]);

       

        // Function Call

        <function_name>([<arguments>]);

}

// Function definition

<return_type><function_name>([<argu_list>]);

{

        <function_body>;

}

Program :

#include <stdio.h>

#include <conio.h>

void add()

{

        int a, b, c;

        clrscr();

        printf("\n Enter Any 2 Numbers : ");

        scanf("%d %d",&a,&b);

        c = a + b;

        printf("\n Addition is : %d",c);

}

void main()

{

        void add();

        add();

        getch();

}

Output :

 Enter Any 2 Numbers : 23 6

 Addition is : 29_

Advantages :

·         It is easy to use.

·         Debugging is more suitable for programs.

·         It reduces the size of a program.

·         It is easy to understand the actual logic of a program.

·         Highly suited in case of large programs.

·         By using functions in a program, it is possible to construct modular and structured programs.