# Fibonacci Series in C Using Function

Previously we have written the Fibonacci series program in C. Now, we will develop the same but using function. In this post, we will write the Fibonacci series in C using the function.

A function is a block of code that performs a specific task. For example, the main is a function and every program execution starts from the main function in C programming. The function is a small program that is used to do a particular task. In C, a big program is divided into several small subroutines/functions/procedures. Hence C is a function-oriented programming language.

The C program is made of one or more pre-defined/user-defined functions. Every program must have at least one function with the name main. The execution of the program always starts from the main function and ends with the main function. The main function can call other functions to do some special task.

In the Fibonacci series, the next element will be 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:- Xn= Xn-1+ Xn-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.

## Display Fibonacci series in C within a range using a function

``````#include<stdio.h>
void fibonacciSeries(int range)
{
int a=0, b=1, c;
while (a<=range)
{
printf("%d\t", a);
c = a+b;
a = b;
b = c;
}
}

int main()
{
int range;

printf("Enter range: ");
scanf("%d", &range);

printf("The fibonacci series is: \n");

fibonacciSeries(range);

return 0;
}``````

Output for different test-cases:-

Enter range: 20
The fibonacci series is:
0 1 1 2 3 5 8 13

Enter range: 50
The fibonacci series is:
0 1 1 2 3 5 8 13 21 34

## Display fibonacci series upto Nth term

``````#include<stdio.h>
void fibonacciSeries(int n)
{
int a=0, b=1, c;
for(int i=0; i<n; i++)
{
printf("%d\t", a);
c = a+b;
a = b;
b = c;
}
}

int main()
{
int term;

printf("Enter the term: ");
scanf("%d", &term);

printf("The fibonacci series is: \n");

fibonacciSeries(term);

return 0;
}``````

Output for different test-cases:-

Enter the term: 5
The fibonacci series is:
0 1 1 2 3

Enter the term: 10
The fibonacci series is:
0 1 1 2 3 5 8 13 21 34

## Find nth term of Fibonacci series in C using function

``````#include<stdio.h>
int fibonacciTerm(int n)
{
int a=0, b=1, c;
for(int i=1; i<n; i++)
{
c = a+b;
a = b;
b = c;
}
return a;
}

int main()
{
int term, result;

printf("Enter term to find: ");
scanf("%d", &term);

result = fibonacciTerm(term);

printf("The fibonacci term is: %d", result);

return 0;
}``````

Output for test-case-1:-

Enter the term to find: 5
The Fibonacci term is: 3

Output for test-case-2:-

Enter the term to find: 10
The Fibonacci term is: 34

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