User Guide > Overview > What Does A Script Look Like?

A problem description script is a readable text file. The contents of the file consist of a number of sections, each identified by a header. The fundamental sections are:

•TITLE	a descriptive label for the output.
•SELECT	user controls that override the default behavior of FlexPDE.
•VARIABLES	here the dependent variables are named.
•DEFINITIONS	useful parameters, relationships or functions are defined.
•EQUATIONS	each variable is associated with a partial differential equation.
•BOUNDARIES	the geometry is described by walking the perimeter of the domain, stringing together line or arc segments to bound the figure.
•MONITORS and PLOTS	desired graphical output is listed, including any combination of CONTOUR, SURFACE, ELEVATION or VECTOR plots.
•END	completes the script.

Note: There are several other optional sections for describing special aspects of the problem. Some of these will be introduced later in this document. Detailed rules for all sections are presented in the FlexPDE Problem Descriptor Reference chapter "The Sections of a Descriptor".

COMMENTS can be placed anywhere in a script to describe or clarify the work. Two forms of comment are available:

•{ Anything inside curly brackets is a comment. }

•! from an exclamation to the end of the line is a comment.

Example:

A simple diffusion equation on a square might look like this:

TITLE 'Simple diffusion equation'

{ this problem lacks sources and boundary conditions }

VARIABLES

DEFINITIONS

k=3 { conductivity }

EQUATIONS

div(k*grad(u)) =0

BOUNDARIES

REGION 1

START(0,0)

LINE TO (1,0) TO (1,1) TO (0,1) TO CLOSE

PLOTS

CONTOUR(u)

VECTOR(k*grad(u))

END

Later on, we will show detailed examples of the development of a problem script.