fun function_set(bits, lines, dots_wide: Int)
	do
		var fs = flag_function_set
		if bits == 8 then
			fs = fs | 16
		else if bits != 4 then abort

		if lines == 2 then
			fs = fs | 8
		else if lines != 1 then abort

		if dots_wide == 10 then
			fs = fs | 4
		else if dots_wide != 8 then abort

		write(true, fs)
	end