This C program prints out the first Fibonacci series (sequence) of N numbers. In mathematics, the Fibonacci numbers are a sequence of numbers named after Leonardo of Pisa, known as Fibonacci. The first number of the sequence is 0, the second number is 1, and each subsequent number is equal to the sum of the previous two numbers of the sequence itself, thus creating the sequence 0, 1, 1, 2, 3, 5, 8, etc. The standard form of writing Fibonacci series is:

xn = xn-1 + xn-2

where:

  • xn is term number “n”
  • xn-1 is the previous term (n-1)
  • xn-2 is the term before that (n-2)
Fibonacci Numbers

Fibonacci Numbers

So this program prints the N numbers of Fibonacci series in C on the screen where N is the integer number entered by the user. This C program prints maximum of 50 Fibonacci numbers.

This program uses the following C Programming topics so go thorough these articles for a better understanding of the program:

#include <stdio.h>

int main(void) {
    //The number of Fibonacci numbers we will print
    int n; 
    // The index of Fibonacci number to be printed next 
    int i; 
    // The value of the (i)th Fibonacci number
    long current; 
    // The value of the (i+1)th Fibonacci number 
    long next; 
    // The value of the (i+2)th Fibonacci number 
    long twoaway; 

    printf("How many Fibonacci numbers do you want to compute? \n");
    scanf("%d", &n);
    
    if (n<=0 || n>50 ) {
        printf("The number should be positive and less than 51.\n");
    }
    else {
        printf("\n\n\tI \t Fibonacci(I) \n\t=====================\n");
        next = current = 1;
        for (i=1; i<=n; i++) {
            printf("\t%d \t %ld\n", i, current);
            twoaway = current+next;
            current = next;
            next = twoaway;
        }
    }
}

Output of the C Program

How many Fibonacci numbers do you want to compute? 
50


	I 	 Fibonacci(I) 
	=====================
	1 	 1
	2 	 1
	3 	 2
	4 	 3
	5 	 5
	6 	 8
	7 	 13
	8 	 21
	9 	 34
	10 	 55
	11 	 89
	12 	 144
	13 	 233
	14 	 377
	15 	 610
	16 	 987
	17 	 1597
	18 	 2584
	19 	 4181
	20 	 6765
	21 	 10946
	22 	 17711
	23 	 28657
	24 	 46368
	25 	 75025
	26 	 121393
	27 	 196418
	28 	 317811
	29 	 514229
	30 	 832040
	31 	 1346269
	32 	 2178309
	33 	 3524578
	34 	 5702887
	35 	 9227465
	36 	 14930352
	37 	 24157817
	38 	 39088169
	39 	 63245986
	40 	 102334155
	41 	 165580141
	42 	 267914296
	43 	 433494437
	44 	 701408733
	45 	 1134903170
	46 	 1836311903
	47 	 2971215073
	48 	 4807526976
	49 	 7778742049
	50 	 12586269025