Siag recognizes two main types of cells, those that contain labels and those that contain expressions.
A label can be any text and is not used in calculations. If the cell starts with a letter instead of an expression character or number (see below), it is automatically assumed to be a label. You can also force a cell to be identified as a label by placing the double quote ( " ) character in front of the text. The double quote is one of the special characters described in the previous section that causes the cell to be processed as a certain type of data. This is the same behavior as other spreadsheets and is useful when a label starts with a number or reserved character.
When a cell is used as a label the Cell Info box next to the cell editor will display "Label:" as shown below.
An expression can be a Scheme LISP, "C" style, Tcl, or Guile command. Go to the next page for more information on expressions.