# Fibonacci Series in C++ using For Loop

Before going to the program first let us understand what is a *Fibonacci Series?*

**Fibonacci Series:**

Fibonacci series is nothing but a Series of Numbers which are found by adding the two preceding(previous) Numbers.

For Example,

0,1,1,2,3,5,8,13,21 is a Fibonacci Series of length 9.

For more understanding you can check out the following link:

https://www.mathsisfun.com/numbers/fibonacci-sequence.html

## Program code to Display Fibonacci Series in C++:

#include<iostream.h> #include<conio.h> void main() { int n,i,f,f1=0,f2=1; clrscr(); cout<<" Enter The Number:"; cin>>n; cout<<" The Fibonacci Series is:"; cout<<" \n"<<f1<<" \n"<<f2; for(i=2;i<n;i++) { f=f1+f2; f1=f2; f2=f; cout<<" \n"<<f; } getch(); }

**Related: **Fibonacci Series in C using For Loop

## Working:

- First the computer reads the value of number of terms for the Fibonacci series from the user.
- Then using for loop the two preceding numbers are added and printed.
- The loop continues till the value of number of terms.

## Step by Step working of the above Program Code:

Let us assume that the Number of Terms entered by the user is 5.

- It assigns the value of n=5 and prints the first two numbers “f1” and “f2” (ie. 0 and 1) on the output screen.
- Then it assigns the value of i=2 in the initialization part of the for loop.
- Then the loop continues till the condition of the for loop is true.

3.1. i<n (2<5), for loop condition is true

f=f1+f2 (f=0+1) So f=1

f1=f2 (f1=1) So f1=1

f2=f (f2=1) So f2=1

print the value of “f” (ie. 1)

i++ (i=i+1) So i=3

3.2. i<n (3<5), for loop condition is true

f=f1+f2 (f=1+1) So f=2

f1=f2 (f1=1) So f1=1

f2=f (f2=2) So f2=2

print the value of “f” (ie. 2)

i++ (i=i+1) So i=4

3.3. i<n (4<5), for loop condition is true

f=f1+f2 (f=1+2) So f=3

f1=f2 (f1=2) So f1=2

f2=f (f2=3) So f2=3

print the value of “f” (ie. 3)

i++ (i=i+1) So i=5

3.4. i<n (5<5), for loop condition is false

comes out of the for loop.

- Thus the program execution is completed.

## Output:

### TO DOWNLOAD THE PROGRAM CODES : CLICK HERE

Thank you very much, that helped a lot!