public MainWindow()
{
// This line must be executed first:
InitializeComponent();
// Own stuff here:
cs = new CStack();
LetterField.Text = "T:\nZ:\nY:\nX:\n▹";
VarLetterField.Text = $"A=\nB=\nC=\nD =\nE=\nF=\nG=\nH=\n▹";
UpdateNumberField();
}