Observe the graph, the graph is adjusted in horizontal segments. The step functions are only adjusted in 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\")