A piecewise function that is defined by a constant value on each part of its domain is called a step function. The following equation is one example of a step function. $f(x) = \begin{cases} 0 & \quad 0\leq x < 1 \\ 2 & \quad 1\leq x < 2 \\ 4 & \quad 2\leq x < 3 \\ 6 & \quad 3\leq x < 4 \end{cases}$ The graph of a step function consists of two or more line segments that are horizontal lines. The function $f(x)$ has four segments.