p	plot:  plots the foam directly to screen.

P [-n <num>] [-hatch] [-ps <filename>] [-hpgl <filename>] [-tek <filename>]
Plot with options: This has a number of optional arguments which may be
used in any combination.  With integer argument '-n <num>', it
plots nXn multiple copies of the periodic box and the argument '-hatch'
causes the Plateau borders to be shaded in.  It is possible to save the
plot to file using one of the last three options: '-ps' for Postscript,
'-hpgl' for HPGL format and '-tek' for Tektronix format.

a	adjust:  this routine allows pending increments to vertices to be
made without invoking equilibration.  However, the usual safeguards
against anomolous structures are called from the equilibration
routine.

e	equilibrate:  incorporate any pending increments and bring the
structure to equilibrium, iterating a maximum of 'maxiter' times.
Convergence is controlled principally via 'areasup' and 'equilsup'.
See command 's'.

E	Equilibrate with plotting:  equilibrates the system, plotting
the system after each iteration. This is very useful in interactive
mode.  Dynamic 'zooming' is also possible---use the mouse buttons.

d	diffuse:  diffuses gas from cell to cell via Von Neumann's law.
The size of this step is determined by the parameter 'diffuserate'.

D	Diffuse with option:  at present identical with command 'd'.

F [-e][-E][-d] f	makefraction:  used to set and alter the
volume-fraction of the system (denoted as 'phi' in usual soap froth
theory).  Options '-e','-E' and '-d' are mutually exclusive and
optional, as implemented.  The -e/-E options select equilibration
without/with plotting respectively---the default is *without* plotting.
The floating point parameter 'f' is a number in [0,1] and sets the new
volume-fraction 'phi'.  Option -d causes the argument 'f' to be
interpreted as an increment to 'phi' instead.
NB:  The algorithm used presently suffers from a flaw which may lead the
program to fail as percolation is approached.

b	boxstrain (Hencky strain):  applies a small increment of
extensional strain to the system.  The step size is determined by the
first occurrence of the command 'B' (see below).  The system is *not*
subsequently equilibrated.  Equilibration must be explicitly requested
using command 'e' for example.

B f	Boxstrain with option:  strain the box, setting the step size
'eps' to be equal to the real number 'f'.  This command ought to be
called before calling command 'b' in order to set 'eps'.

h, H	help:  displays this help message.

g, G	graphics interactive:  Opens an X window for using interactive
graphics and a simple user interface.

i	infowrite:  writes a line of data to the file 'info.pb' (and
also, possibly, prints some data on the screen).  This is envisaged as
the primary avenue of data output from the program and the file
'info.pb' is stored in tab-delimited format.  Which
data is to be output must be selected using the command 'I' *before* the
first occurrence of thes command 'i'.  The file 'info.pb' is
automatically closed upon exiting the program.

I -c, I [-w] <dataname>	Infowrite with options:  the command
'I -c' simply closes the file 'info.pb'.  Setting 'I <dataname>'
requests that 'dataname' be one of the data fields listed in 'info.pb'.
With the optional argument 'w' this information will also be printed to
the screen whenever command 'i' is encountered.

List of 'datanames'...
muside		mu2 of sides distribution
rhoside		distribution of sides
muarea		mu2 of area distribution
arean		distribution of areas
bside		distribution of sides of Plateau borders
netenergy	energy of network
minenergy	energy of equivalent disks of network
henckyeps	present value of Hencky strain parameter
elosscount	a count of how many edges have been lost in the present
		run (not physically significant)
bpinchcount	a count of the number of border pinches in this run (not
		physically significant)
phi		present bolume-fraction
nbar		average number of sides, counting all cells
edgefrac	average fraction of an edge obscured by Plateau borders
z		average co-ordination of a cell.  This is *almost* the
		same as 'nbar' except that here free-floating cells are
		not included in the average.
arootbar	the average of the square root of cell area---indicative
		of the average cell radius

r	read foam:  reads in a system from the default file 'foam.pb'.

R <filename>	Read foam:  reads the system in from the file 'filename'.

w	write foam:  writes the system to the default file 'foam.pb'.

W <filename>	Write foam:  writes the system to the file 'filename'.

n	hexnet:  initialises the system as a unit cell of a hexagonal
lattice (which contains two hexagonal cells).  It is initialised with
Plateau borders which cover 0.4 of the cell-cell edges.

N nx ny f	hexNet:  initialises the system as a hexagonal nxXny
lattice (containing 2 nxXny cells).  Parameter 'f' gives the fraction of
a cell-cell edge covered by Plateau borders.

v	voronoi network:  initialise the system as a Voronoi network
with default parameters and the maximum number of cells possible
(this command is *not* particularly recommended)

V [-r f] n	Voronoi network:  request a Voronoi network with 'n'
cells.  The optional argument '-r' allows you to specify the hard-disk
radius 'f'.  The parameter 'f' lies in the range [0,1] where 0
represents maximum disorder.  In practice 'f' cannot be too close to
1.0 .  It is possible to specify a different random seed if a new
starting point for the network is desired.  See the command 'S'.

S -w <setname>, S <setname> f	Set:  when used with the option '-w'
gives the present value of the parameter 'setname'.  The second syntax
sets parameter 'setname' to the new value 'f'.
The current list of settable parameters is:
vdamp, vvdamp, pdamp, bpdamp, bprelax, minbfrac, maxbfrac, lengthdelta,
pressuredelta, diffuserate, areasup, bareasup, maxdv, maxdvv, equilsup,
minvvlen, filmwid, cosminang, rfrac, notopol, minareasup, maxiter,
vorseed.

q	quit  quit the program.

x	exit:  exit the program, unless this command occurs within a set
of braces.

Zooming: When in interactive graphics mode (after typing the command
'g' or 'G') there is a zoom feature available via the mouse.  By
clicking the left mouse button you can zoom into a location and by
clicking the right mouse button you can zoom out again.  The middle
mouse button changes the centre of the viewing port without changing the
scale.  In order to restore the original default scalings just click on
the button 'reset plot'.

Repetitive Loops Using Braces:
	Simple repetitive looping may be obtained with this simple
syntax
	{...<commands>...}n
A group of commands is enclosed in curly braces immediately
followed by an integer.  The integer determines the number of times that
the commands within the braces are executed.  These loops may be
nested.


Spacing of Commands:
	The general rule is that spaces are optional, except where necessary
to remove ambiguity.  Command loops enclosed in braces may spread over several
input lines.