At a Meeting of the Corporate Audit Committee Attended by the General

At a meeting of the corporate audit committee attended by the general manager of the products division (A.Smith)and the internal audit manager (P.Marks),the following dialogue took place between Smith and R.Jones (chair of the corporate audit committee):
Jones: Ms.Marks has suggested that the internal audit department conduct an examination of the computer activities of the products division.
Smith: I don't know much about the technicalities of computers,but the division has some of the best computer people in the company.
Jones: Do you know whether the internal controls we have implemented are satisfactory?
Smith: I suppose they are.No one has complained.What's so important about controls anyway,as long as the system works? I don't even know what type of controls we should have for our system.
Jones: Ms.Marks,can you explain the objective of computer controls and provide us some examples?
Required:
Address Ms.Marks' response to the following points:
a.State the principal objective of achieving control over (1)input,(2)processing,and (3)output.
b.Provide examples of (1)input controls,(2)processing controls,and (3)output controls.