What is the Fibonacci sequence?

In the Fibonacci series, each number is the sum of the two previous numbers. The first two numbers in the Fibonacci series are 0 and 1.

The sequence Fn of Fibonacci numbers is defined by the recurrence relation:

Fn = Fn-1 + Fn-2  ( where, n > 1)

with seed values

F0 = 0 and F1 = 1.

The beginning of the sequence is thus:

0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, ……..

Algorithm to generate Fibonacci sequence using C program:

1. Get the Fibonacci series limit from the user, say n.
2. Assign “preValue1” = 0, “preValue2” = 1.
3. Assign the addition of”preValue1 and preValue2” to “next”.
   next = preValue1 + preValue2
4. Swap “preValue2” to “preValue1” and “next ” to “preValue2”.
5. Repeat steps 3 and 4 till n.

See the C program to generate the Fibonacci sequence based on the number of terms entered by the user.

#include <stdio.h>
int main()
{
    int num, i = 0, next, preValue1 = 0, preValue2 = 1;

    printf("Enter no. of terms: ");
    scanf("%d",&num);

    if(num < 0)
    {
        printf("Enter valid number\n");
    }
    else
    {
        while(i < num)
        {
            if(i <= 1)
            {
                next = i;
            }
            else
            {
                next = preValue1 + preValue2;
                preValue1 = preValue2;
                preValue2 = next;
            }
            printf("%d \t", next);
            i++;
        }
    }


    return 0;
}

Output:

Enter no. of terms: 5
0 1 1 2 3