Zero-order hold (ZOH)

Zero-order hold (ZOH) devices convert sampled signals to continuous-time signals for analyzing
sampled continuous-time systems.
G(s) =10/(s^2 + 3s + 10)

G = tf(10,[1 3 10]); % create transfer function
Gd = c2d(G, 0.1) % zoh is the default method
step(G,'--',Gd,'-')



 http://www.mathworks.com/help/control/continuous-and-discrete-time-conversion.html