FAQs in C: Generate Fibonacci Series

Generating the Fibonacci series involves producing a sequence where each number is the sum of the two preceding ones, starting from 0 and 1. Here’s the algorithm, C program, and detailed explanation for generating the Fibonacci series.

Algorithm to Generate Fibonacci Series

Step 1: Start
Step 2: Input: Read the number of terms n (positive integer) to generate in the Fibonacci series.

Step 3: Process:
        - Initialize variables a, b, and c.
        - a and b represent the first two terms of the Fibonacci series    
          (a = 0 and b = 1).
        - Print a (first term of the series).
        - Print b (second term of the series).
   
        For i from 3 to n:
          - Calculate c = a + b.
          - Print c.
          - Update a to b and b to c for the next iteration.

Step 4: Output: Display the Fibonacci series up to n terms.
Step 5: End

C Program to Generate Fibonacci Series

#include <stdio.h>

int main() {
    int n, a = 0, b = 1, c, i;

    // Step 2: Read the number of terms from the user
    printf("Enter the number of terms in Fibonacci series: ");
    scanf("%d", &n);

    // Step 3: Generate and print Fibonacci series
    printf("Fibonacci Series up to %d terms:\n", n);

    // Print the first two terms of Fibonacci series
    printf("%d %d ", a, b);

    // Generate and print the rest of the series
    for (i = 3; i <= n; i++) {
        c = a + b;   // Calculate next term
        printf("%d ", c);  // Print the next term
        a = b;       // Update a to b
        b = c;       // Update b to c
    }

    // Step 5: End
    return 0;
}

Explanation of Each Step

Include Header:

#include <stdio.h>

• This line includes the standard input-output library.

Main Function:

int main() {

• The main function is the entry point of the C program.

Variable Declaration:

int n, a = 0, b = 1, c, i;

• Four integer variables are declared: n to store the number of terms in the Fibonacci series, a and b to store the first two terms (0 and 1 respectively), c to store the next term in the series, and i for iteration.

Reading Input:

printf("Enter the number of terms in Fibonacci series: ");
scanf("%d", &n);

• printf prompts the user to enter the number of terms (n) in the Fibonacci series.
• scanf reads the integer and stores it in the variable n.

Generating and Printing Fibonacci Series:

printf("Fibonacci Series up to %d terms:\n", n);

• printf displays a message indicating the number of terms for the Fibonacci series.

Printing First Two Terms:

printf("%d %d ", a, b);

• Prints with the initial values of a (0) and b (1), which are the first two terms of the Fibonacci series.

Generating the Rest of the Series:

for (i = 3; i <= n; i++) {
    c = a + b;   // Calculate next term
    printf("%d ", c);  // Print the next term
    a = b;       // Update a to b
    b = c;       // Update b to c
}

• The for loop iterates from 3 to n (inclusive).
• In each iteration:
  • c is calculated as the sum of a and b, which is the next term in the Fibonacci series.
  • c is printed using printf.
  • a is updated to b (a now holds the previous value of b).
  • b is updated to c (b now holds the current value of c).

End:

return 0;

• This line indicates successful completion of the program.

This program effectively generates and prints the Fibonacci series up to n terms as specified by the user. It uses iterative logic to calculate each subsequent term based on the previous two terms (a and b).