Give an example of Piecewise-Defined Functions?

Step 1
By a piecewise defined function, a function of the form
${\displaystyle f\left(x\right)=\{\begin{array}{cc}g\left(x\right)& \text{if}x\in A\\ h\left(x\right)& \text{if}x\in A\end{array}\}}$
Where g(x) h(x)
Are any fixed function.
Step 2
For example:
${\displaystyle f\left(x\right)=\{\begin{array}{cc}1& \text{if}x\ge 0\\ 0& \text{if}x<0\end{array}\}}$
Called unit step function, is an example for piecewise defined function and also has many applications in signal processing systems.