Basic Language -Lecture

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
/*http://www.youtube.com/watch?v=XR3nkD6Ikrc
 http://bgcoder.com/Contests/Practice/Index/8#4*/
namespace _20.BasicLang
{
    class Program
    {

        static StringBuilder output = new StringBuilder(); //reusable
        static List<string> allCommands = new List<string>();
        static void Main(string[] args)
        {
            ReadInput();
            ConvertInputToCommands();
            RunCommands();
            Console.WriteLine(output.ToString());
        }

        private static void RunCommands()
        {
            output.Clear();
            for (int i = 0; i < allCommands.Count; i++)//get line of commands ended with ; and split by ) to get sub comd
            {
                int allLoops = 1;
                string[] subConmmands = allCommands[i].Split(new char[]{')'},StringSplitOptions.RemoveEmptyEntries);
                foreach (var command in subConmmands)
                {
                    string currentCommand = command.TrimStart();
                    if (currentCommand.StartsWith("EXIT"))
                    {
                        //Environment.Exit(0);
                        return;
                    }
                    else if (currentCommand.StartsWith("PRINT"))
                    {
                        int parmStart = currentCommand.IndexOf("(") + 1;
                        string content = currentCommand.Substring(parmStart);

                        for (int j = 0; j < allLoops; j++)
                        {
                            output.Append(content);
                        }

                    }
                    else if (currentCommand.StartsWith("FOR"))
                    {
                        int parmStart=currentCommand.IndexOf("(")+1;
                        string allParams = currentCommand.Substring(parmStart);
                        if (allParams.Contains(","))//FOR(a, b)
                        {
                            string[] loopParams = allParams.Split(',');
                            int a = int.Parse(loopParams[0]);
                            int b = int.Parse(loopParams[1]);

                            allLoops = allLoops * (b - a + 1);
                        }
                        else //FOR(a)
                        {
                            int value = int.Parse(allParams);
                            allLoops = allLoops * value;
                        }
                    }
                }
            }
        }

        private static void ConvertInputToCommands()
        {
            string allInput = output.ToString();
            output.Clear();
            foreach (var symbol in allInput)
            {
                output.Append(symbol);
                if (symbol==';')
                {
                    allCommands.Add(output.ToString());//find and hold all commands
                    output.Clear();
                }
            }
        }

        private static void ReadInput()
        {
            while (true)
            {
                string line = Console.ReadLine();
                output.Append(line);
                if (line.Contains("EXIT;"))
                {
                    break;
                }
            }


        }
    }
}