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What is Operator C Comma Operator C Arithmetic Operators C Relational Operators C Logical Operators C Bitwise Operators C Conditional Operators C : : Operator C Operator Priority

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What is Control Statement C if Statement C if else Statement C Nested if Statement C Else if Statement C Break Statement C Continue Statement C Switch Statement C Goto Statement


What is Control Loop C for Loop C Nested for Loop C while Loop C Nested while Loop C do while Loop C Nested do while loop


What is Function C User Defined Functions C Recursion C Passing Parameters


Scope C Local Scope C Global Scope

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What is Storage Class C Auto C Extern C Static C Register


What is Array C One Dimensional Array C Two Dimensional Array C Multi Dimensional Array C Arrays Of Strings


What is String C String Functions


What is Pointer C Pointers Arithmetic C Pointer to Pointer C Pointers and Arrays C Pointers and Strings C Pointer to Functions Void Pointers Null Pointers C Null and Void Pointer


What is Structure C Struct within Struct C Array within Structure C Pointer to Structure C Structure and Function C Enum C Bitfield Structure C Type def


What is Union


What is File C read a file C write a file C File Handling C Error Handling C Low Level Disk I/O C Other file functions

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What is Memory Allocation C Malloc() C Calloc() C Free() C Realloc() C Coreleft()

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The ones who are crazy enough to think they can change the world are the ones who do.
- Steve Jobs

C Fibonacci Series

Mathematically, Fibonacci numbers are the sequence of numbers, where every numbers after 0 and 1 are the summation of previous two numbers. For example consider the following series.

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

here 5 is the summation of 2 and 3, where as 13 is the summation of 5 and 8 and so on.

Interesting Facts about Fibonacci Series

  • Though Leonardo Pisano Bogollo (1170 - 1250) introduced Fibonacci series, it was used in India hundreds of years before.
  • Fibonacci number sequence are in the format of even number followed by 2 odd numbers i.e) even, odd, odd, even, odd, odd ....
  • Leonardo Pisano Bogollo was the son of Bonacci, thus the name fibonacci were derived.
  • Nov - 23 i.e) 11 - 23 is the only day in fibonacci series.
c fibonacci calender

Pictorical Representation of Fibonacci Series

c fibonacci series

C Program - Fibonacci Series

Let us write a c program to display n fibonacci numbers, here n represents user entered number.

#include <stdio.h>
int main()
int a = 0, b = 1, c, i, num;
printf("Enter a number: ");
if(num < 1)
printf("\nInvalid inuput ");
else if(num > 1)
printf("\t %d \n\t %d ", a, b);
for(i = 3;i <= num;i++)
c = a + b;
a = b;
b = c;
printf("\n\t %d ", c);
printf("%d ", a);
return 0;
Enter a number : 5
0 1 1 2 3


Here, variable a = 0 and b = 1, if user enter number is greater than 1 i.e) 4. for-loop will iterate twice , for the first time c=1, a=1 and b=1 and append the value in c to 0 1 i.e) 0 1 1. Then for the next for-loop iteration c = 2, a = 1, b = 2 and append the value in c to 0 1 1 i.e) 0 1 1 2.

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