using System;
using System.Windows.Forms;
using System.ComponentModel;
using System.Drawing;

class Calculator:Form
{
  const int BUTTON_VERTICALSPACING=5;
  const int BUTTON_HORIZONTALSPACING=3;

  const int MEMORY_BUTTON_WIDTH=35;
  const int MEMORY_BUTTON_HEIGHT=35;
  const int MEMORY_BUTTONY=70;
  const int MEMORY_BUTTONX=5;
  
  const int DIGIT_BUTTON_WIDTH=35;
  const int DIGIT_BUTTON_HEIGHT=35;
  const int DIGIT_BUTTONY=MEMORY_BUTTONY;
  const int DIGIT_BUTTONX=MEMORY_BUTTONX+MEMORY_BUTTON_WIDTH+BUTTON_HORIZONTALSPACING+5;

  const int DISPLAY_HEIGHT=25;

  const int OTHER_BUTTON_HEIGHT=DIGIT_BUTTON_HEIGHT-10;
  const int OTHER_BUTTON_WIDTH=60;
  const int OTHER_BUTTONY=5+DISPLAY_HEIGHT+10;
  const int OTHER_BUTTONX=DIGIT_BUTTONX;

  const int FORM_HEIGHT=260;
  const int FORM_WIDTH=250;



  Button[] btnDigitOperator=new Button[20];
  Button[] btnMemory=new Button[4];
  Button[] btnOther=new Button[3];

  Label lblDisplay;
  Label lblMemory;

  string[,] DigitCaption=new String[5,4]{{"7","4","1","0"},{"8","5","2","+/-"},{"9","6","3","."},{"/","*","-","+"},{"sqrt","%","1/x","="}};
  string[] MemoryCaption={"MC","MR","MS","M+"};
  string[] OtherCaption={"BackSpace","CE","C"};

  static double BufferValue=0.0;
  static double Operand1=0.0;
  static double Operand2=0.0;

  static string Operator="";

  //if true then the number does not have integral part.
  static bool IsFraction=false;

  //if digit pressed just after operator then clear display and
  //display only the clicked digit otherwise do concatenation
  static bool IsOperatorClicked=false; 

  public Calculator()
  {

    lblDisplay=new Label();
    lblDisplay.Text="0.";
    lblDisplay.BackColor=Color.White;
    lblDisplay.Location=new Point(5,5);
    lblDisplay.Size=new Size(FORM_WIDTH-20,DISPLAY_HEIGHT);
    lblDisplay.BorderStyle=System.Windows.Forms.BorderStyle.Fixed3D;
    lblDisplay.TextAlign=ContentAlignment.MiddleRight;
    this.Controls.Add(lblDisplay);

    lblMemory=new Label();
    lblMemory.Text="";
    lblMemory.BackColor=this.BackColor;
    lblMemory.Location=new Point(MEMORY_BUTTONX,OTHER_BUTTONY);
    lblMemory.Size=new Size(MEMORY_BUTTON_WIDTH,OTHER_BUTTON_HEIGHT);
    lblMemory.BorderStyle=System.Windows.Forms.BorderStyle.Fixed3D;
    lblMemory.TextAlign=ContentAlignment.MiddleCenter;
    this.Controls.Add(lblMemory);

    // Adding Memory Buttons
    for(int i=0;i<btnMemory.Length;i++)
    {
      btnMemory[i]=new Button();
      btnMemory[i].ForeColor=Color.Red;
      btnMemory[i].Text=MemoryCaption[i];
      btnMemory[i].Size=new Size(MEMORY_BUTTON_WIDTH,MEMORY_BUTTON_HEIGHT);
      if(i==0)
      {
        btnMemory[i].Location=new Point(MEMORY_BUTTONX,MEMORY_BUTTONY);
      }
      else
      {
        btnMemory[i].Location=new Point(MEMORY_BUTTONX,MEMORY_BUTTONY + i*MEMORY_BUTTON_HEIGHT  + i*BUTTON_VERTICALSPACING);
      }
      btnMemory[i].Click+=new EventHandler(Memory_Click);
      this.Controls.Add(btnMemory[i]);
    }

    // Adding Digit/Operator Buttons
    int btnIndex=0;    
    for(int i=DigitCaption.GetLowerBound(0);i<=DigitCaption.GetUpperBound(0);i++)
    {
      for(int j=DigitCaption.GetLowerBound(1);j<=DigitCaption.GetUpperBound(1);j++)
      {
        btnDigitOperator[btnIndex]=new Button();
        btnDigitOperator[btnIndex].Text=DigitCaption[i,j];
        btnDigitOperator[btnIndex].ForeColor=Color.Blue;
        btnDigitOperator[btnIndex].Size=new Size(DIGIT_BUTTON_WIDTH,DIGIT_BUTTON_HEIGHT);
        int buttonX=DIGIT_BUTTONX+i*DIGIT_BUTTON_WIDTH+i*BUTTON_HORIZONTALSPACING;
        if(j==0)
        {
          btnDigitOperator[btnIndex].Location=new Point(buttonX,DIGIT_BUTTONY);
        }
        else
        {
          btnDigitOperator[btnIndex].Location=new Point(buttonX,DIGIT_BUTTONY + j*DIGIT_BUTTON_HEIGHT+j*BUTTON_VERTICALSPACING);
        }

        if(i==DigitCaption.GetUpperBound(0)-1)
          btnDigitOperator[btnIndex].ForeColor=Color.Red;
        if(i==DigitCaption.GetUpperBound(0) && j==DigitCaption.GetUpperBound(1))
          btnDigitOperator[btnIndex].ForeColor=Color.Red;

        btnDigitOperator[btnIndex].Click+=new EventHandler(DigitOpertor_Click);
        this.Controls.Add(btnDigitOperator[btnIndex++]);
      }
    }
      // Adding Other Buttons
      for(int i=0;i<btnOther.Length;i++)
      {
        btnOther[i]=new Button();
        btnOther[i].ForeColor=Color.Red;
        btnOther[i].Text=OtherCaption[i];
        if(i==0)
        {
          btnOther[i].Location=new Point(OTHER_BUTTONX,OTHER_BUTTONY);
          btnOther[i].Size=new Size(OTHER_BUTTON_WIDTH+10,OTHER_BUTTON_HEIGHT);
        }
        else
        {
          btnOther[i].Location=new Point((2-i)*5+10+OTHER_BUTTONX + i*OTHER_BUTTON_WIDTH  + i*BUTTON_HORIZONTALSPACING,OTHER_BUTTONY);
          btnOther[i].Size=new Size(OTHER_BUTTON_WIDTH-10,OTHER_BUTTON_HEIGHT);
        }
        btnOther[i].Click+=new EventHandler(OtherButton_Click);
        this.Controls.Add(btnOther[i]);        
      }

      this.Size=new Size(FORM_WIDTH,FORM_HEIGHT);
      this.MaximizeBox=false;
      this.Text="Calculator";
  }

  public void Memory_Click(object sender,EventArgs eArgs)
  {
    switch(((Button)sender).Text)
    {
      case "MR":
        lblDisplay.Text=BufferValue.ToString()+".";
        break;
      case "MS":
        BufferValue=Double.Parse(lblDisplay.Text);
        lblMemory.Text="M";
        break;
      case "M+":
        try
        {
          BufferValue+=Double.Parse(lblDisplay.Text);
        }
        catch(Exception)
        {
          BufferValue=0.0;
        }
        break;
      case "MC":
        BufferValue=0.0;
        lblMemory.Text="";
        break;
      }
  }

  public void DigitOpertor_Click(object sender,EventArgs eArgs)
  {
    string Caption=((Button)sender).Text;
    bool IsError=false;
    switch(Caption)
    {
      case "+":
      case "-":
      case "*":
      case "/":
        Operand1=Double.Parse(lblDisplay.Text);
        Operator=Caption;
        IsOperatorClicked=true;
        IsFraction=false;
        break;
      case "=":
        Operand2=Double.Parse(lblDisplay.Text);
        IsOperatorClicked=false;
        switch(Operator)
        {
          case "+":
            try
            {
              lblDisplay.Text=(Operand1+Operand2).ToString();
            }
            catch(Exception)
            {
              IsError=true;
              lblDisplay.Text="Error.";
            }
            break;
          case "-":
            try
            {
              lblDisplay.Text=(Operand1-Operand2).ToString();
            }
            catch(Exception)
            {
              IsError=true;
              lblDisplay.Text="Error.";
            }
            break;            
          case "*":
            try
            {
              lblDisplay.Text=(Operand1*Operand2).ToString();
            }
            catch(Exception)
            {
              IsError=true;
              lblDisplay.Text="Error.";
            }
            break;                        
          case "/":
            try
            {
              lblDisplay.Text=(Operand1/Operand2).ToString();
            }
            catch(Exception)
            {
              IsError=true;
              if(Operand2==0)
                lblDisplay.Text="Cannot Divide by Zero.";
              else
                lblDisplay.Text="Error.";
            }
            break;                        
        }
        if(!IsError && lblDisplay.Text.IndexOf(".")<0)
        {
            lblDisplay.Text+=".";
        }
        break;
      case "+/-":
        try
        {
          if(lblDisplay.Text!="0.")
          {
            if(lblDisplay.Text.Substring(lblDisplay.Text.Length-1)==".")
              lblDisplay.Text=(-Double.Parse(lblDisplay.Text)).ToString()+".";
            else
              lblDisplay.Text=(-Double.Parse(lblDisplay.Text)).ToString();
          }
        }
        catch(Exception)
        {
          lblDisplay.Text="Error.";
        }
        break;
      case ".":
        IsFraction=true;
        break;
      case "1/x":
        try
        {
          if(lblDisplay.Text!="0.")
            lblDisplay.Text=(1.0/Double.Parse(lblDisplay.Text)).ToString();
          if(lblDisplay.Text.IndexOf(".")<0)
            lblDisplay.Text+=".";
         }
         catch(Exception)
         {
          lblDisplay.Text="Error.";
         }
        break;
      case "%":
        break;
      case "sqrt":
        try
        {
          lblDisplay.Text=Math.Sqrt(Double.Parse(lblDisplay.Text)).ToString();
          if(lblDisplay.Text.IndexOf(".")<0)
            lblDisplay.Text+=".";
        }
        catch(Exception)
        {
          lblDisplay.Text="Error.";
        }
        break;
      default:
        if(IsOperatorClicked)
        {
          lblDisplay.Text="0.";
        }
        if(lblDisplay.Text!="0.")
        {
          if(!IsFraction)
          {
            lblDisplay.Text=lblDisplay.Text.Substring(0,lblDisplay.Text.Length-1) + Caption + ".";
          }
          else
          {
            lblDisplay.Text=lblDisplay.Text.Substring(0,lblDisplay.Text.Length) + Caption;
          }
        }
        else
        {
          if(!IsFraction)
          {
            lblDisplay.Text=Caption + ".";
          }
          else
          {
            lblDisplay.Text=lblDisplay.Text+Caption;
          }
        }
        IsOperatorClicked=false;
        break;
    }

  }

  public void OtherButton_Click(object sender,EventArgs eArgs)
  {
    switch(((Button)sender).Text)
    {
      case "CE":
      case "C":
        lblDisplay.Text="0.";
        IsFraction=false;
        break;
      default:
        if(lblDisplay.Text.Length>2)
        {
          if(lblDisplay.Text.Substring(lblDisplay.Text.Length-1)==".")
          {
            lblDisplay.Text=lblDisplay.Text.Substring(0,lblDisplay.Text.Length-2) + ".";
          }
          else
          {
            lblDisplay.Text=lblDisplay.Text.Substring(0,lblDisplay.Text.Length-1);            
          }
        }
        else
        {
          IsFraction=false;
          lblDisplay.Text="0.";
        }
        break;
    }
  }

  public static void Main()
  {
    Application.Run(new Calculator());
  }
}