C program to print fibonacci series upto n terms

Write a C program to print Fibonacci series up to n terms using loop. How to generate Fibonacci series up to n terms using loops in C programming. Logic to print Fibonacci series in a given range in C programming.

Example

Input

Input number of terms: 10

Output

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

Fibonacci series

Required knowledge

Basic C programming, If statement, For loop, While loop

What is Fibonacci series?

Fibonacci series is a series of numbers where the current number is the sum of previous two terms. For Example: 0, 1, 1, 2, 3, 5, 8, 13, 21, ... , (n-1th + n-2th)

Logic to print Fibonacci series upto n terms

Step by step descriptive logic to print n Fibonacci terms.

  1. Input number of Fibonacci terms to print from user. Store it in a variable say terms.
  2. Declare and initialize three variables, I call it as Fibonacci magic initialization. a=0, b=1 and c=0.

    Here c is the current term, b is the n-1th term and a is n-2th term.

  3. Run a loop from 1 to terms, increment loop counter by 1. The loop structure should look like for(i=1; i<=term; i++). It will iterate through n terms
  4. Inside the loop copy the value of n-1th term to n-2th term i.e. a = b.

    Next, copy the value of nth to n-1th term b = c.

    Finally compute the new term by adding previous two terms i.e. c = a + b.

  5. Print the value of current Fibonacci term i.e. c.

Program to print Fibonacci series up to n terms

/**
 * C program to print Fibonacci series up to n terms
 */

#include <stdio.h>

int main()
{
    int a, b, c, i, terms;

    /* Input number from user */
    printf("Enter number of terms: ");
    scanf("%d", &terms);

    /* Fibonacci magic initialization */
    a = 0;
    b = 1;
    c = 0;

    printf("Fibonacci terms: \n");

    /* Iterate through n terms */
    for(i=1; i<=terms; i++)
    {
        printf("%d, ", c);

        a = b;     // Copy n-1 to n-2
        b = c;     // Copy current to n-1
        c = a + b; // New term
    }

    return 0;
}

Move a step forward and advance your programming skills by learning this program using recursive approach.

Learn more - Program to find nth Fibonacci series using recursion.

Output

Enter number of terms: 10
Fibonacci terms: 
0, 1, 1, 2, 3, 5, 8, 13, 21, 34,

Let us modify the above code to print Fibonacci series between a given range.

Program to print Fibonacci series in given range

/**
 * C program to print Fibonacci series in given range
 */

#include <stdio.h>

int main()
{
    int a, b, c, start, end;

    /* Input a number from user */
    printf("Enter starting term: ");
    scanf("%d", &start);
    printf("Enter end term: ");
    scanf("%d", &end);

    /* Fibonacci magic initialization */
    a = 0;
    b = 1;
    c = 0;

    printf("Fibonacci terms: \n");

    /* Iterate through terms */
    while(c <= end)
    {

        /* If current term is greater than start term */
        if(c >= start) 
        {
            printf("%d, ", c);
        }

        a = b;     // Copy n-1 to n-2
        b = c;     // Copy current to n-1
        c = a + b; // New term
    }

    return 0;
}

Output

Enter starting term: 4
Enter end term: 30
Fibonacci terms:
5, 8, 13, 21,

Happy coding 😉

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