C program to display fibonacci sequence has been shown here. For example if the total no terms is $10$, we get the first $10$ fibonacci numbers i.e. $0, 1, 1, 2, 3, 5, 8, 13, 21, 34$. The following section covers the iterative approach to find fibonacci sequence. The algorithm, pseudocode and time complexity of the program have been shown below.

## 1. Algorithm to display fibonacci sequence

1. Take number of terms n as input.

2. Intialize a counter variable say count = 0

3. Assign the first two fibonacci numbers to variables a, b i.e. a = 0 and b = 1

4. Display a and b.

5. Perform t = a + b and display t as next fibonacci.

6. Perform a = b and b = t

7. Perform count = count + 1.

8. If count < n - 2, go to step 5 else stop the process.

## 2. Pseudocode to display fibonacci sequence

Input : No of terms $n$

Output : First $n$ no fibonacci

1. Procedure fibonacciSequence($n$):

2. $count \leftarrow 0$

3. $a \leftarrow 0$

4. $b \leftarrow 1$

5. Display $a, b$

6. Repeat until $count < n - 2$:

7. $t \leftarrow a + b$

8. Display $t$

9. $a \leftarrow b$

10.$b \leftarrow t$

11.$count \leftarrow count + 1$

12. End Procedure

## 3. Time complexity to display fibonacci sequence

Time Complexity: O(n)

Where n is the total no of terms in fibonacci sequence.

## 4. C Program & output to display fibonacci sequence using iteration

Code has been copied
/******************************
alphabetacoder.com
C program to display fibonacci
sequence using iteration
*******************************/

#include <stdio.h>

int main() {
// declare variables
int n, count = 0, a, b, t;

// take input of the no of terms
printf("Enter the no of terms = ");
scanf("%d", & n);

// intialize the first two number of the sequence
a = 0;
b = 1;

printf("First %d fibonacci numbers: ", n);

// display first two fibonacci
if (n >= 2)
printf("%d, %d", a, b);
// display only first fibonacci
else if (n == 1)
printf("%d", a);

//now calculate the remaining n-2 numbers in the sequence
while (count < n - 2) {
// calculate next fibonacci
t = a + b;
//display next fibonacci
printf(", %d", t);

//assign values for next iteration
a = b;
b = t;

// increment the counter
count = count + 1;
}

return 0;
}


Output

#### Case 1:

Enter the no of terms = 10

First 10 fibonacci numbers: 0, 1, 1, 2, 3, 5, 8, 13, 21, 34

#### Case 2:

Enter the no of terms = 2

First 2 fibonacci numbers: 0, 1

#### Case 3:

Enter the no of terms = 20

First 20 fibonacci numbers: 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 3 77, 610, 987, 1597, 2584, 4181

## 5. C Program & output to display fibonacci sequence using recursion

Code has been copied
/******************************
alphabetacoder.com
C program to display fibonacci
sequence using recursion
*******************************/

#include <stdio.h>

// recursive function to display
// fibonacci sequence
void fibonacci(int a, int b, int count) {
if (count == 1) // exit condition
printf("%d ", a); // print current term
else if (count > 1) {
printf("%d ", a); // print current term
// call function
fibonacci(b, a + b, count - 1);
}
}

int main() {
// declare variables
int n, count = 0;

// take input of the no of terms
printf("Enter the no of terms = ");
scanf("%d", & n);

// display n no of fibonacci
printf("First %d fibonacci numbers: ", n);
// call the function
// pass value of the first two
// term and total no of fibonacci
fibonacci(0, 1, n);

return 0;
}


Output

#### Case 1:

Enter the no of terms = 10

First 10 fibonacci numbers: 0, 1, 1, 2, 3, 5, 8, 13, 21, 34

#### Case 2:

Enter the no of terms = 2

First 2 fibonacci numbers: 0, 1