Print Fibonacci Series

#include <stdio.h>

int main() {
    int n, firstTerm = 0, secondTerm = 1, nextTerm;

    // Asking the user for the number of terms
    printf("Enter the number of terms: ");
    
    // Input validation for non-negative integers
    if (scanf("%d", &n) != 1 || n < 0) {
        printf("Invalid input. Please enter a non-negative integer.\n");
        return 1;  // Returning 1 indicates abnormal termination
    }

    // Edge cases for Fibonacci sequence
    if (n == 0) {
        printf("Fibonacci series: No terms to display.\n");
    } else if (n == 1) {
        printf("Fibonacci series: %d\n", firstTerm);
    } else {
        // Printing the first two terms
        printf("Fibonacci series: %d, %d", firstTerm, secondTerm);

        // Loop to calculate the next terms
        for (int i = 3; i <= n; ++i) {
            nextTerm = firstTerm + secondTerm;  // The next term is the sum of the previous two terms
            printf(", %d", nextTerm);  // Printing the next term

            firstTerm = secondTerm;  // Update firstTerm to the next term
            secondTerm = nextTerm;  // Update secondTerm to the next term
        }
        printf("\n");  // Newline for output formatting
    }

    return 0;  // Returning 0 indicates successful termination
}

Explanation:

1. Including the standard input-output library: We include stdio.h to use functions like printf and scanf for input and output.cCopy code#include <stdio.h>
2. Main function: Program execution begins from the main() function.cCopy codeint main() { ... }
3. Declaring variables:
   • n stores the number of terms the user wants to print in the Fibonacci series.
   • t1 is initialized to 0, which represents the first term in the Fibonacci series.
   • t2 is initialized to 1, which represents the second term in the Fibonacci series.
   • nextTerm will store the next number in the sequence as we compute it.
   cCopy codeint n, t1 = 0, t2 = 1, nextTerm;
4. User input: We prompt the user to input the number of terms using printf and then use scanf to store this value in the variable n.cCopy codeprintf("Enter the number of terms: "); scanf("%d", &n);
5. Printing the Fibonacci series:
   • We use a for loop that runs n times, which means it will print the first n terms of the Fibonacci series.
   • Inside the loop:
     • We print t1, which is the current term in the series.
     • We then calculate the next term in the Fibonacci series by adding t1 and t2.
     • After calculating nextTerm, we update t1 to t2 and t2 to nextTerm to move the sequence forward.
   • This process is repeated until we print the required number of terms.
   cCopy codefor (int i = 1; i <= n; ++i) { printf("%d ", t1); nextTerm = t1 + t2; t1 = t2; t2 = nextTerm; }
6. Returning 0: The program returns 0 to indicate that it has executed successfully.cCopy code

OUTPUT

Enter the number of terms: 10
Fibonacci Series: 0 1 1 2 3 5 8 13 21 34

Summary:

It uses a simple loop and updates the terms of the series iteratively.

The Fibonacci series is a sequence where each number is the sum of the two preceding ones, starting with 0 and 1.

The program prints the Fibonacci series up to the number of terms specified by the user.