In most cases, FlexPDE notation is simple text as in a programming language.        

•Differentiation, such as du/dx, is denoted by the form dx(u). All active coordinate names are recognized, as are second derivatives like dxx(u) and differential operators Div, Grad and Curl.

•Names are NOT case sensitive.  "F" is the same as "f".

•Comments can be placed liberally in the text.  Use { } to enclose comments or ! to ignore the remainder of the line.

Note: See the Problem Descriptor Reference chapter on Elements for a full description of  FlexPDE notation.