Observe the graph, the graph contains horizontal segments. The step functions contains only horizontal segments. So, the function of given graph is step function.
The function of given graph is S for step.
![\"\"](\"http://www.mathskey.com/userfiles/image/steps_images/step1.JPG\")
![\"\"](\"http://www.mathskey.com/userfiles/image/steps_images/solution.JPG\")