Example: Calculate Quadratic Equation Roots in C

// Calculate Quadratic Equation Roots
#include <stdio.h>
#include <math.h> // Required for sqrt() function

int main() {
    // Step 1: Declare variables for coefficients and roots
    double a, b, c;
    double discriminant, root1, root2;
    double realPart, imagPart;
    int status_indicator;

    // Step 2: Get input from the user for coefficients
    printf("Enter coefficients a, b and c: ");
    scanf("%lf %lf %lf", &a, &b, &c);

    // Step 3: Check if 'a' is zero, as it's not a quadratic equation then
    if (a == 0) {
        printf("Error: 'a' cannot be zero for a quadratic equation.\n");
        // For a=0, it becomes a linear equation bx + c = 0, x = -c/b
        if (b != 0) {
            printf("It's a linear equation. Root = %.2lf\n", -c / b);
        } else {
            printf("Invalid coefficients (a=0, b=0).\n");
        }
        return 1; // Indicate an error
    }

    // Step 4: Calculate the discriminant
    discriminant = b * b - 4 * a * c;

    // Step 5: Determine the status based on discriminant value
    if (discriminant > 0) {
        status_indicator = 1; // Real and distinct roots
    } else if (discriminant == 0) {
        status_indicator = 0; // Real and equal roots
    } else {
        status_indicator = -1; // Complex roots
    }

    // Step 6: Use switch case to handle different root types
    switch (status_indicator) {
        case 1: // Case for real and distinct roots (discriminant > 0)
            root1 = (-b + sqrt(discriminant)) / (2 * a);
            root2 = (-b - sqrt(discriminant)) / (2 * a);
            printf("Discriminant = %.2lf\n", discriminant);
            printf("Root 1 = %.2lf\n", root1);
            printf("Root 2 = %.2lf\n", root2);
            break;

        case 0: // Case for real and equal roots (discriminant == 0)
            root1 = -b / (2 * a);
            printf("Discriminant = %.2lf\n", discriminant);
            printf("Root 1 = Root 2 = %.2lf\n", root1);
            break;

        case -1: // Case for complex roots (discriminant < 0)
            realPart = -b / (2 * a);
            imagPart = sqrt(-discriminant) / (2 * a);
            printf("Discriminant = %.2lf\n", discriminant);
            printf("Root 1 = %.2lf + %.2lfi\n", realPart, imagPart);
            printf("Root 2 = %.2lf - %.2lfi\n", realPart, imagPart);
            break;
    }

    return 0;
}