Do not a knot splines force continuity at each knot?

Question

Given a cubic spline equation $S(x) = S_0(x), S_1(x), S_2(x)$

Does it follow the continuity rules where $S_0(x_2) = S_1(x_2)$ and $S_1(x_3) = S_2(x_3)$ assuming x1 is the starting point and $x_4$ is the end point?