C Program to Generate Fibonacci Series

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• Write a C program to Generate Fibonacci Series.
• Write a C program to Calculate Fibonacci Series.

Explanation

A series of numbers in which each number is the sum of the two preceding or previous numbers is called Fibonacci Series.

For example, Fibonacci series upto 7 numbers is 1, 1, 2, 3, 5, 8, 13.

In above example, first 2 numbers (1, 1) are printed directly as there are no preceding numbers. But after that, i.e the 3rd number (2) is the sum of 1st and 2nd number (1+1=2). Similarly to get 4th number, we add 2nd and 3rd number. (i.e., 1+2=3). You can use this pattern to find fibonacci series upto any number.

Mathematical expression to find Fibonacci number is :

Fn=Fn-1+Fn-2

i.e. To get nth position number, you should add (n-2) and (n-1) position number.

Program

#include <stdio.h>
int main() {
  int i, n;
  int a = 0, b = 1;
  int sum = a + b;
  printf("Enter the number of terms: ");
  scanf("%d", &n);
  printf("Fibonacci Series: %d, %d, ", a, b);
  for (i = 3; i <= n; i++) {
    printf("%d, ", sum);
    a = b;
    b = sum;
    sum = a + b;
  }
  return 0;
}

                 // Suman-Chakrabortty.web.app
                // dev-suman-ch.blogspot.com

Output:
Enter Fibonacci Range: 10
Fibonacci Series: 0, 1, 1, 2, 3, 5, 8, 13, 21, 34.

Algorithm

Step 1: Start 

Step 2: Declare variable a, b, c, n, i

Step 3: Initialize variable a=0, b=1 and  i=2 

Step 4: Read n from user 

Step 5: Print a and b 

Step 6: Repeat until i<=n : 

           Step 6.1: c=a+b 

           Step 6.2: print c 

           Step 6.3: a=b, b=c 

           Step 6.4: i=i+1 

Step 7: Stop

FlowChart

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