**C TUTORIAL**

#

**C PROGRAMS**

Function

➤ Introduction to Function

➤ User-defined Functions

➤ Recursion in C

➤ Storage Classes in C

➤ Scope of Variables

Function Programs in C

➤ Functions Examples in C

➤ Add 2 Numbers Function

➤ Find Sum of N numbers

➤ Largest of Three Numbers

➤ Add Subtract Multiply Divide

➤ Calculator Program Functions

➤ Factorial Program Function

➤ GCD of Two Numbers

➤ Find Power of a Number

➤ Find Reverse a Number

➤ Fibonacci Series Function

➤ Prime Number Function

➤ Palindrome Number in C

➤ Armstrong Number in C

Recursion Programs in C

➤ Recursion Examples in C

➤ Fibonacci Series

➤ Find Factorial

➤ Find GCD or HCF

➤ LCM Using Recursion

➤ Tricky C Programs

Here, we will write a program to find the Fibonacci series using recursion in C language, and also we will find the nth term of the Fibonacci series. Prerequisites:- Recursion in C Programming Language

Another example of recursion is a function that generates Fibonacci numbers. Named after an Italian mathematician, Leonardo Fibonacci, who lived in the early thirteenth century. Fibonacci numbers are a series in which each number is the sum of the previous two numbers.

In the Fibonacci series, the next element is the sum of the previous two elements. The Fibonacci sequence is a series of numbers where a number is found by adding up the two numbers before it.

Starting with 0 and 1, the sequence goes 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, and so forth. Written as a rule, the expression is X_{n}= X_{n-1}+ X_{n-2}

By definition, the first two numbers in the Fibonacci sequence are either 1 and 1, or 0 and 1, depending on the chosen starting point of the sequence, and each subsequent number is the sum of the previous two.

The base case for finding factorial

General case for finding factorial **fibonacci(0) = 0 fibonacci(1) = 1**

**fibonacci**(n) = **fibonacci**(n-1) + **fibonacci**(n-2)

```
Algorithm:- fibonacci(n)
if (n<=1)
then return n
else
return fibonacci(n-1) + fibonacci(n-2)
```

## C program to Find Nth Fibonacci term using Recursion

Program description:- **Write a C program to find the nth Fibonacci number using recursion techniques.**

```
#include<stdio.h>
// recursive function for finding nth Fibonacci term
int
```**fibonacci**(int n)
{
if(n<=0)
return n; //base case
else //general case
return **fibonacci**(n-1)+**fibonacci**(n-2);
}
int main()
{
int num;
printf("Which term of Fibonacci series
you want to find: ");
scanf("%d",&num);
printf("%dth term is %d\n",num,
fibonacci(num));
return 0;
}

Output for the different test-cases:-

Which term of Fibonacci series you want to find: `5`

5th term is 5

Which term of Fibonacci series you want to find: `7`

7th term is 13

Which term of Fibonacci series you want to find: `10`

10th term is 55

## Find first N numbers in Fibonacci series

Program description:- **Write a C program to display first n numbers in the Fibonacci series using recursion in C. **

```
#include<stdio.h>
int
```**fibonacci**(int n)
{
if(n<=0)
return n; //base case
else //general case
return **fibonacci**(n-1)+**fibonacci**(n-2);
}
int main()
{
int num;
printf("How many numbers of Fibonacci
series you want to print: ");
scanf("%d",&num);
printf("Fibonacci series:\n");
for(int i=0; i<num; i++)
{
printf("%d\t",fibonacci(i));
}
return 0;
}

Output for the different test-cases:-

How many numbers you want to print: `5`

Fibonacci series:` 0 1 1 2 3`

How many numbers you want to print: `10`

Fibonacci series:** 0 1 1 2 3 5 8 13 21 34 **

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