clone

        private void btnpocl(object sender, EventArgs e)
        {

            if (ccal.Length > 0)
            {
                ccal = ccal.Remove(ccal.Length - 1, 1);
            }

            txtbout.Text = ccal;
        }

        private void btnpocl(object sender, EventArgs e)
        {

            if (ccal.Length > 0)
            {
                ccal = ccal.Remove(ccal.Length - 1, 1);
            }

            txtbout.Text = ccal;
        }