private void subtract_Click(object sender, EventArgs e)
 {
     calculator.Number_entered(Convert.ToDouble(display.Text));
     display.Text       = calculator.Subtraction_entered();
     isNewNumberEntered = true;
     temp_History      += display.Text + "-";
 }
 private void Subtract_btn_Click(object sender, EventArgs e)
 {
     Op_lbl.Text  = Subtract_btn.Text;
     Lhs_lbl.Text = textBox1.Text;
     Tape_txtBox.AppendText(Lhs_lbl.Text + "\n");
     textBox1.Clear();
     calc.Subtraction_entered();
 }