function unitstep(np)
% Generates and plots x[n] = u[n];
% ------------------------------------------
% unitstep(np)
%np - points count
if np < 0
	error('argument np must satisfy np >0')
end
n = [0:np];
x = [ones(1,np+1)];
stem(n,x,'filled');
xlabel('n');
ylabel('x[n]');
title('D-T Unit Step Signal')
axis ([-1 np+1 0 2]);
grid;
