# XPP will disregard lines starting with '#'
u'=u*(1-u)-a*u*v
v'=v*(1-v)-b*u*v  
# list the parameters
par a=1.2,b=.8  
# initial conditions
init u=0.5,v=0.5 
# the rest is not required, can be entered or adjusted within XPP
# axis boundaries
@ xlo=-0.1,ylo=-0.1,xhi=1.4,yhi=1.2
# figure axis variables
@ xp=u,yp=v
# total time for the ODE to be solved for
@ total=100
# mesh size for computing the nullclines
@ Nmesh=200 
done