Quadratic Equation Program

 1// Program    : Quadratic Equation
 2// Author     : Prof. Krofchok
 3// Date       : Fall 2025
 4// Description: This program solves quadratic equations having real roots.
 5
 6#include <cmath>      // provides 'sqrt' module
 7#include <iostream>
 8
 9void welcome();
10void input_data(double &a, double &b, double &c);
11void perform_calculations(double a, double b, double c,
12    double &root1, double &root2);
13void output_results(double a, double b, double c,
14    double root1, double root2);
15
16int main()
17{
18    double a, b, c;       // coefficients of Ax^2 + Bx + C = 0
19    double root1, root2;  // roots of the equation
20
21    welcome();
22    input_data(a, b, c);
23    perform_calculations(a, b, c, root1, root2);
24    output_results(a, b, c, root1, root2);
25}
26
27//
28// An output module that displays information about the program.
29//
30void welcome()
31{
32    std::cout << "This program computes and displays the"  << std::endl;
33    std::cout << "roots of a second-degree polynomial"     << std::endl;
34    std::cout << "equation of the form Ax^2 + Bx + C = 0." << std::endl;
35    std::cout                                              << std::endl;
36    std::cout << "You will be prompted to input the three" << std::endl;
37    std::cout << "coefficients A, B, and C."               << std::endl;
38    std::cout                                              << std::endl;
39    std::cout << "This program acts unpredictably when"    << std::endl;
40    std::cout << "given coefficients that do not produce"  << std::endl;
41    std::cout << "real-valued roots."                      << std::endl;
42    std::cout                                              << std::endl;
43}
44
45//
46// An input module that gets the coefficients of a second-degree polynomial
47// in the form Ax^2 + Bx + C
48//
49void input_data(double &a, double &b, double &c)
50{
51    std::cout << "Enter coefficient 'A': ";
52    std::cin >> a;
53    std::cout << "Enter coefficient 'B': ";
54    std::cin >> b;
55    std::cout << "Enter coefficient 'C': ";
56    std::cin >> c;
57}
58
59//
60// A processing module that computes the real-valued roots of the equation,
61// given its coefficients.
62//
63void perform_calculations(double a, double b, double c,
64    double &root1, double &root2)
65{
66    double discriminant;
67
68    discriminant = (b * b) - (4 * a * c);
69    root1 = (-b + sqrt(discriminant)) / (2 * a);
70    root2 = (-b - sqrt(discriminant)) / (2 * a);
71}
72
73//
74// An output module that displays the equation and its roots.
75//
76void output_results(double a, double b, double c,
77    double root1, double root2)
78{
79    std::cout << std::endl;
80    std::cout << "The roots of the equation "
81              << a << "x^2 + "
82              << b << "x + "
83              << c << std::endl;
84    std::cout << "are " << root1 << " and " << root2 << std::endl;
85}