codes

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

namespace calculator
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();

}
private void Form1_Load(object sender, EventArgs e)
{

}
double a;
double b;
double ans;
int ch;
public bool flag=false;
public bool zflag=false;
float temp;
public bool dflag = false;


private void button1_Click(object sender, EventArgs e)
{

if (flag == false)
{
if (dflag == false)
{
if (zflag == false)
{
a = 1;
zflag = true;
}
else
a = (a * 10) + 1;
}
else
{
temp = temp * 10;
a = a + (1 / temp);

}
textBox1.Text = a.ToString();
}
else
{
if (dflag == false)
{
if (zflag == false)
{
b = 1;
zflag = true;
}
else
b = (b * 10) + 1;
}
else
{
temp = temp * 10;
b = b + (1 / temp);

}
textBox1.Text = b.ToString();
}
}

private void button2_Click(object sender, EventArgs e)
{
if (flag == false)
{
if (dflag == false)
{
if (zflag == false)
{
a = 2;
zflag = true;
}
else
a = (a * 10) + 2;
}
else
{
temp = temp * 10;
a = a + (2 / temp);
}
textBox1.Text = a.ToString();
}
else
{
if (dflag == false)
{
if (zflag == false)
{
b = 2;
zflag = true;
}
else
b = (b * 10) + 2;
}
else
{
temp = temp * 10;
b = b + (2 / temp);

}
textBox1.Text = b.ToString();
}
}

private void button3_Click(object sender, EventArgs e)
{
if (flag == false)
{
if (dflag == false)
{
if (zflag == false)
{
a = 3;
zflag = true;
}
else
a = (a * 10) + 3;
}
else
{
temp = temp * 10;
a = a + (3 / temp);

}
textBox1.Text = a.ToString();
}
else
{
if (dflag == false)
{
if (zflag == false)
{
b = 3;
zflag = true;
}
else
b = (b * 10) + 3;
}
else
{
temp = temp * 10;
b = b + (3 / temp);

}
textBox1.Text = b.ToString();
}
}
private void button4_Click(object sender, EventArgs e)
{
if (flag == false)
{
if (dflag == false)
{
if (zflag == false)
{
a = 4;
zflag = true;
}
else
a = (a * 10) + 4;
}
else
{
temp = temp * 10;
a = a + (4 / temp);
}
textBox1.Text = a.ToString();
}
else
{
if (dflag == false)
{
if (zflag == false)
{
b = 4;
zflag = true;
}
else
b = (b * 10) + 4;
}
else
{
temp = temp * 10;
b = b + (4 / temp);
}
textBox1.Text = b.ToString();
}
}

private void button5_Click(object sender, EventArgs e)
{
if (flag == false)
{
if (dflag == false)
{
if (zflag == false)
{
a = 5;
zflag = true;
}
else
a = (a * 10) + 5;
}
else
{
temp = temp * 10;
a = a + (5 / temp);
}
textBox1.Text = a.ToString();
}
else
{
if (dflag == false)
{
if (zflag == false)
{
b = 5;
zflag = true;
}
else
b = (b * 10) + 5;
}
else
{
temp = temp * 10;
b = b + (5 / temp);

}
textBox1.Text = b.ToString();
}
}

private void button6_Click(object sender, EventArgs e)
{
if (flag == false)
{
if (dflag == false)
{
if (zflag == false)
{
a = 6;
zflag = true;
}
else
a = (a * 10) + 6;
}
else
{
temp = temp * 10;
a = a + (6 / temp);
}
textBox1.Text = a.ToString();
}
else
{
if (dflag == false)
{
if (zflag == false)
{
b = 6;
zflag = true;
}
else
b = (b * 10) + 6;
}
else
{
temp = temp * 10;
b = b + (6 / temp);
}
textBox1.Text = b.ToString();
}
}

private void button7_Click(object sender, EventArgs e)
{

if (flag == false)
{
if (dflag == false)
{
if (zflag == false)
{
a = 7;
zflag = true;
}
else
a = (a * 10) + 7;
}
else
{
temp = temp * 10;
a = a + (7 / temp);

}
textBox1.Text = a.ToString();
}
else
{
if (dflag == false)
{
if (zflag == false)
{
b = 7;
zflag = true;
}
else
b = (b * 10) + 7;
}
else
{
temp = temp * 10;
b = b + (7 / temp);
}
textBox1.Text = b.ToString();
}
}

private void button8_Click(object sender, EventArgs e)
{
if (flag == false)
{
if (dflag == false)
{
if (zflag == false)
{
a = 8;
zflag = true;
}
else
a = (a * 10) + 8;
}
else
{
temp = temp * 10;
a = a + (8 / temp);
}
textBox1.Text = a.ToString();
}
else
{
if (dflag == false)
{
if (zflag == false)
{
b = 8;
zflag = true;
}
else
b = (b * 10) + 8;
}
else
{
temp = temp * 10;
b = b + (8 / temp);
}
textBox1.Text = b.ToString();
}
}

private void button9_Click(object sender, EventArgs e)
{

if (flag == false)
{
if (dflag == false)
{
if (zflag == false)
{
a = 9;
zflag = true;
}
else
a = (a * 10) + 9;
}
else
{
temp = temp * 10;
a = a + (9 / temp);

}
textBox1.Text = a.ToString();

}
else
{
if (dflag == false)
{
if (zflag == false)
{
b = 9;
zflag = true;
}
else
b = (b * 10) + 9;
}
else
{
temp = temp * 10;
b = b + (9 / temp);
}
textBox1.Text = b.ToString();
}
}

private void button10_Click(object sender, EventArgs e)
{
if (flag == false)
{
if (dflag == false)
{
if (zflag == false)
{
a = 0;
zflag = true;
}
else
a = a * 10;
}
else
{
if (zflag == false)
{
temp = temp * 10;
a = a;
zflag = true;
}
else
{
temp = temp * 10;
a = a;
}
}
textBox1.Text = a.ToString();
}
else
{
if (dflag == false)
{
if (zflag == false)
{
b = 0;
zflag = true;
}
else
b = b * 10;
}
else
{
if (zflag == false)
{
temp = temp * 10;
b = b;
zflag = true;
}
else
{
temp = temp * 10;
b = b;
}
}
textBox1.Text = b.ToString();
}
}

private void button12_Click(object sender, EventArgs e)
{
flag = true;
dflag = false;
zflag = false;
ch = 1;
}

private void button13_Click(object sender, EventArgs e)
{
flag = true;
dflag = false;
zflag = false;
ch = 2;
}

private void button14_Click(object sender, EventArgs e)
{
flag = true;
dflag = false;
zflag = false;
ch = 3;
}

private void button15_Click(object sender, EventArgs e)
{
flag = true;
dflag = false;
zflag = false;
ch = 4;
}

private void button16_Click(object sender, EventArgs e)
{
switch (ch)
{
case 1:
ans = a + b;
break;
case 2:
ans = a - b;
break;
case 3:
ans = a * b;
break;
case 4:
ans = a / b;
break;
}
textBox1.Text = ans.ToString();
dflag = false;
}

private void button17_Click(object sender, EventArgs e)
{
a = 0;
b = 0;
flag = false;
zflag = false;
dflag = false;
textBox1.Text = "0";
}

private void button11_Click(object sender, EventArgs e)
{
dflag = true;
temp = 1;
}

}
}