There are many important mathematical series and one of them is the Fibonacci series. It is used for learning recursion in programming. Recursion means a function recursively calls itself during the execution of a program.

This program is compiled using Dev-C++ version 4 compiler on a Windows 7 64-bit system, you can use any other standard C compiler to compile the program and it will work.

This article is intended for intermediate learners of C programming language, so you must be familiar with basic C concepts like functions, variables, operators, and expressions.

### Problem Definition

In mathematics, the whole number means all positive numbers starting with 0. Any term in Fibonacci series takes a sum of previous two terms. The formula for the nth term of Fibonacci series is given below.

`f`_{n} = f_{n-1}+ f_{n-2}

The first few terms of the series are as follows

```
0, 1, 1, 2, 3, 5, 8, 13, 21, 34, ...
```

### Flowchart

### Program Code

```
/* Program to calculate Fibonacci Series */
# include < stdio.h >
#include < stdlib.h >
main ()
{
int n;
void fib ();
printf ("Number of terms to be generated?");
scanf ("%d", & n);
printf ("%d", n);
printf ("\n\nFibonacci sequence up to %d terms :\n\n");
fib(n);
printf("\n");
system("PAUSE");
return 0;
}
void fib(int n)
{
static long int f1 = 0, f2 = 1, sum;
if (n > 0)
{
sum = f1 + f2;
f1 = f2;
printf("%5d", sum);
f2 = sum;
fib(n - 1);
} }
```

### Output

The output of the Fibonacci series is given below.