tokens: A customer brings in a defective computer and the CRS checks the defect and hands out a repair cost calculation back . If the customer decides that the costs are acceptable , the process continues , otherwise she takes her computer home unrepaired . The ongoing repair consists of two activities , which are executed , in an arbitrary order . The first activity is to check and repair the hardware , whereas the second activity checks and configures the software . After each of these activities , the proper system functionality is tested . If an error is detected another arbitrary repair activity is executed , otherwise the repair is finished .