# C program to print Fibonacci series

Category: C Program

Learn how to write a C program to print the Fibonacci series up to n terms. This guide includes an explanation of the Fibonacci sequence, a step-by-step algorithm, and complete code examples.

The Fibonacci series is a sequence of numbers where each number is the sum of the two preceding ones, typically starting with 0 and 1. It is a classic example often used to teach recursion and iterative programming techniques. In this article, we will explore how to write a C program to print the Fibonacci series up to a specified number of terms, n.

## Understanding the Fibonacci Series

The following recurrence relation defines the Fibonacci series:

The first few terms of the Fibonacci series are:

0, 1, 1, 2, 3, 5, 8, 13, 21, 34, ...

## Algorithm to Generate Fibonacci Series

To generate the Fibonacci series up to n terms, we can use the following steps:

1. Input the number of terms n.
2. Initialize the first two terms of the series as 0 and 1.
3. Use a loop to calculate each subsequent term as the sum of the previous two terms.
4. Print each term as it is calculated.

## Write a C program to print Fibonacci series

Here is the complete C program to print the Fibonacci series up to n terms:

``````#include <stdio.h>

int main() {
int n, first = 0, second = 1, next, i;

// Input the number of terms
printf("Enter the number of terms: ");
scanf("%d", &n);

printf("Fibonacci series up to %d terms:\n", n);

// Print the first two terms of the series
if (n >= 1) printf("%d\n", first);
if (n >= 2) printf("%d\n", second);

// Calculate and print the rest of the terms
for (i = 3; i <= n; i++) {
next = first + second;
printf("%d\n", next);
first = second;
second = next;
}

return 0;
}
``````

Output

``````Enter the number of terms: 7
Fibonacci series up to 7 terms:
0
1
1
2
3
5
8
``````

## Explanation of the Code

1. Input the Number of Terms:
• `scanf("%d", &n);` reads the number of terms n from the user.
2. Initialization:
• The first two terms are initialized as `first = 0` and `second = 1`.
3. Printing the First Two Terms:
• The program checks if n is greater than or equal to 1 or 2 and prints the first two terms accordingly.
4. Calculating and Printing the Remaining Terms:
• The `for` loop starts from the 3rd term and continues up to the ( n )-th term.
• In each iteration, `next` is calculated as the sum of `first` and `second`.
• The `first` and `second` values are then updated for the next iteration.

## Example Runs

### Example 1

``````Enter the number of terms: 5
Fibonacci series up to 5 terms:
0
1
1
2
3
``````

### Example 2

``````Enter the number of terms: 10
Fibonacci series up to 10 terms:
0
1
1
2
3
5
8
13
21
34
``````