C#

using System;
using System.Collections.Generic;
using System.Text;
using System.Diagnostics;

namespace hard
{
    class Program
    {
        static void Main(string[] args)
        {
            Program app = new Program();
        }

        Program()
        {
            bool ok = false
            double[] w = new double[25];
            double[] l = new double[25];
            double[] u = new double[25];
            double[] z = new double[25];
            double ft = 0.0, fx = 0.0, alpha = 0.0, h = 0.0, k = 0.0, vv = 0.0, t = 0.0, x = 0.0;
            int n = 0, m = 0, m1 = 0, m2 = 0, n1 = 0, flag = 0, i1 = 0, i = 0, j = 0 ;
            input(ref ok,ref fx,ref ft,ref alpha,ref n,ref m);
            
            if (ok)
            {
                m1 = m - 1;
                m2 = m - 2;
                //    n1 = n - 1;
                /* step 1 */
                h = fx / m;
                k = ft / n;
                vv = alpha * k / (h * h);
                /* step 2 */
                for (i = 1; i <= m1; i++) w[i - 1] = F(i * h);
                /* step 3 */
                l[0] = 1.0 - 2.0 * vv;
                u[0] = vv / l[0];
                /* step 4 */
                for (i = 2; i <= m2; i++)
                {
                    l[i - 1] = 1.0 - 2.0 * vv - vv * u[i - 2];
                    u[i - 1] = vv / l[i - 1];
                }
                /* step 5 */
                l[m1 - 1] = 1.0 - 2.0 * vv - vv * u[m2 - 1];
                /* step 6 */
                for (j = 1; j <= n; j++)
                {
                    /* step 7 */
                    /* current t(j) */
                    //   t = j * k;
                    z[0] = w[0] / l[0];
                    /* step 8 */
                
                    for (i = 2; i <= m1; i++)
                        z[i - 1] = (w[i - 1] - vv * z[i - 2]) / l[i - 1];
                    /* step 9 */
                    w[m1 - 1] = z[m1 - 1];
                    /* step 10 */
                    for (i1 = 1; i1 <= m2; i1++)
                    {
                        i = m2 - i1 + 1;
                        w[i - 1] = z[i - 1] - u[i - 1] * w[i];
                    }
                }
                /* step 11 */
                output(ft, x, m1,ref w, h);
            }
            
        }

        
        private double F(double X)
        {
            double f;
            f = 0.3061 * X * X -2.1286*X+38.11;
            return f;
        }

        private void input(ref bool ok,ref double fx, ref double ft, ref double alpha, ref int n, ref int m )
        {
            Console.Write("Has the function F been created immediately (Y/N) : ");
            string sonuc = Console.ReadLine();
            
            if (sonuc.ToUpper() == "Y")
            {
                Console.WriteLine("The lefthand endpoint on the X-axis is 0.");
                ok = false;
                while (!ok)
                {
                    Console.Write("Input the righthand endpoint on the X-axis: ");
                    fx = Convert.ToDouble(Console.ReadLine());
                    if (fx < 0.0)
                        Console.WriteLine("Must be positive number.");
                    else
                        ok = true;
                }
                ok = false;
                while (!ok)
                {
                    Console.Write("Input the maximum value of the time variable T : ");
                    ft = Convert.ToDouble(Console.ReadLine());
                    if (ft < 0.0)
                        Console.WriteLine("Must be positive number.");
                    else
                        ok = true;
                }
                Console.Write("Input the constant alpha: ");
                alpha = Convert.ToDouble(Console.ReadLine());
                Console.WriteLine("Input integer m = number of intervals");                                              
                Console.WriteLine("input N = number of time intervals");
                Console.WriteLine("Note :must be m>3 ve n>0 ");
                ok = false;
                while (!ok)
                {
                    Console.Write("m (>3) = ");
                    m = Convert.ToInt32(Console.ReadLine());
                    Console.Write("n (>0) = ");
                    n = Convert.ToInt32(Console.ReadLine());
                    if (m <= 2 || n <= 0)
                    {
                        Console.WriteLine("Numbers are not within correct range.");
                    }
                    else
                    {
                        ok = true;
                    }
                }
            }
            else
            {
                Console.WriteLine("The program will end so that the function F can be created.");
                ok = false;
            }
        }

        public void output(double ft, double x, int m1, ref double[] w, double h)
        {
            System.IO.StreamWriter oup;
            System.IO.TextWriter tmp = Console.Out;
            Console.WriteLine("Choice of output method.");
            Console.WriteLine("1. Output to screen");
            Console.WriteLine("2. Output to text file");
            int flag = Convert.ToInt32(Console.ReadLine());
            if (flag == 2)
            {
                
                Console.WriteLine("Sample:   D:\\1.txt");
                string name = Console.ReadLine();
                try
                {
                    
                    oup = new System.IO.StreamWriter(name);
                    Console.SetOut(oup);
                    write(ft, x, m1, ref w, h);
                    oup.Close();
                }
                catch (System.IO.IOException expc)
                {
                    Console.WriteLine(expc.Message + " file dont extract.");
                }
            }
            else
            {
                write(ft, x, m1, ref w, h);
            }


        }

        private void write(double ft, double x, int m1, ref double[] w, double h)
        {
            
            Console.WriteLine("I\tX(I)\tW(X(I),{0:#.#})", ft);
               for (int i = 1; i <= m1; i++)
            {
                x = i * h;
                Console.WriteLine("{0:#.##}\t{1:#.###}\t\t{2:#.###}", i, x, w[i - 1]);
            }
        }
    }
}