functionally cohesive module | a module that inputs meteorological data from weather stations and satellites and generates an atmospheric model that other systems can use to generate weather forecasts | the user | function parameters, but they can also include files or some other stream of data | side effects such as updating a database or creating a new file | cohesive module | a simple return value or a more complex data structure | the services of other modules, but the called modules must preserve the functional cohesion |