You can use the Tools/Insert variable menu option or
the button on the main toolbar to do this - see the figure below.
The little red square represents variables
The Turing programs and Visual Turing use Greek symbols for the variables.
For a easier use of them, in Visual Turing the names of the Greek symbols
are written with the symbol. The variables are used to retain symbols.
The loading of a variable is made by placing it as the left operand in
a condition on an arrow- see Modifying the condition of the arrow