Controlling is the last managerial function in which the top management of an organization compares the standard performance with the actual performance. The deviations found in this process helps the management in the planning process to take the corrective actions to improve the performance of the company and also to minimize those deviations. It is a continuous process which is closely linked to planning process and is generally performed at the end of the every financial year.
To read more about controlling process, follow this link: http://en.wikipedia.org/wiki/Control_(management)