Let's make a compiler; from Pascal to C#

[output]

MOVE #1,D0
MOVE D0,-(SP)
MOVE #2,D0
ADD (SP)+,D0
MOVE D0,-(SP)
MOVE #3,D0
ADD (SP)+,D0
LEA a(PC),A0
MOVE D0,(A0)

[input]

a=1+2+3

[source]

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace Cradle
{
    public partial class frmCradle : Form
    {
        public frmCradle()
        {
            InitializeComponent();
        }

        private void btnCompile_Click(object sender, EventArgs e)
        {
            string input = tbxInputCmd.Text;
            if (input.Length > 0)
            {
                Parser myparser = new Parser(input);
                myparser.Assignment();
                tbxOutput.Text = myparser.Output;
            }
            else
            {
                MessageBox.Show("입력 수식이 없습니다");
            }
        }
    }
}

----------------------------------------------------------------------------------------------

using System;
using System.Text;
using System.IO;
using System.Media;
using System.Windows.Forms;

namespace Cradle
{

    class Parser
    {
        private StringBuilder outBuffer;
        private StringReader InBuffer;
        private char look;

        public char Look
        {
            get { return look; }
            set { look = value; }
        }

        public string Output
        {
            get { return outBuffer.ToString(); }
            set { ; }
        }

        // constructor
        public Parser(string msg)
        {
            Console.WriteLine(msg);
            outBuffer = new StringBuilder();
            InBuffer = new StringReader(msg);
            GetChar();
        }

        // method
        protected void GetChar()
        {
            int b;
            b = InBuffer.Read();
            Look = (char)b;
        }

        protected void Error(string msg)
        {
            SystemSounds.Beep.Play();
            MessageBox.Show(msg);
        }

        protected void Abort(string msg)
        {
            Error(msg);
            throw new ArgumentException();
        }

        protected void Expected(string msg)
        {
            Abort(msg + " Expected");
        }

        protected void SkipWhite()
        {
            while (Look == '\t' || Look == ' ')
                GetChar();
        }

        protected string GetNum()
        {
            string value = "";
            if (Char.IsNumber(Look) == false)
                Expected("Integer");
            while (Char.IsNumber(Look))
            {
                value += Look;
                GetChar();
            }
            SkipWhite();
            return value;
        }

        protected string GetName()
        {
            string token = "";
            if (Char.IsLetter(Look) == false)
                Expected("Name");
            while (Char.IsLetter(Look) || Char.IsNumber(Look))
            {
                token += Look;
                GetChar();
            }
            SkipWhite();
            return token;
        }

        protected void Emit(string msg)
        {
            outBuffer.Append(msg);
        }

        protected void EmitLn(string msg)
        {
            outBuffer.AppendLine(msg);
        }

        protected void Match(char ch)
        {
            if (Look == ch)
            {
                GetChar();
                SkipWhite();
            }
            else
            {
                Expected("\'" + ch + "\'");
            }
        }

        protected void Ident()
        {
            string name;
            name = GetName();
            if (Look == '(')
            {
                Match('(');
                Match(')');
                EmitLn("BSR " + name);
            }
            else
            {
                EmitLn("MOVE " + name + "(PC),D0");
            }
        }

        protected void Multiply()
        {
            Match('*');
            Factor();
            EmitLn("MULS (SP)+,D0");
        }

        protected void Divide()
        {
            Match('/');
            Factor();
            EmitLn("MOVE (SP)+,D1");
            EmitLn("DIVS D0,D1");
            EmitLn("MOVE D1,D0");
        }

        protected void Add()
        {
            Match('+');
            Term();
            EmitLn("ADD (SP)+,D0");
        }

        protected void Subtract()
        {
            Match('-');
            Term();
            EmitLn("SUB (SP)+,D0");
            EmitLn("NEG D0");
        }

        protected void Factor()
        {
            if (Look == '(')
            {
                Match('(');
                Expression();
                Match(')');
            }
            else if (Char.IsLetter(Look))
            {
                Ident();
            }
            else
            {
                EmitLn("MOVE #" + GetNum() + ",D0");
            }
        }

        protected void Term()
        {
            Factor();
            while (Look == '*' || Look == '/')
            {
                EmitLn("MOVE D0,-(SP)");
                switch (Look)
                {
                    case '*':
                        Multiply();
                        break;
                    case '/':
                        Divide();
                        break;
                    default:
                        Expected("Mulop");
                        break;
                }
            }
        }

        protected void Expression()
        {
            if (Look == '+' || Look == '-')
                EmitLn("CLR D0");
            else
                Term();
            while (Look == '+' || Look == '-')
            {
                EmitLn("MOVE D0,-(SP)");
                switch (Look)
                {
                    case '+':
                        Add();
                        break;
                    case '-':
                        Subtract();
                        break;
                    default:
                        Expected("Addop");
                        break;
                }
            }
        }

        public void Assignment()
        {
            string name;
            name = GetName();
            Match('=');
            Expression();
            EmitLn("LEA " + name + "(PC),A0");
            EmitLn("MOVE D0,(A0)");
        }
    }

}