function(begin.age = 30, slope = 0.0004)
{
#Program input.tau()
#
#Simple linear model.
#
	ages <- 1:aa - 0.5
	tau <- pmax(rep(0, times = aa), slope * (ages - begin.age))
	tau <- tau[1:aa]	#truncate if necessary
	names(tau) <- ages
	write.ascii(compute.tau)
	tau
}