Dec 1998 SD206: Systems Design (Question 3)

(a)	In the context of an information system, what are the controls and why are they needed?	[2]
	Controls are functions that are designed to build the required level of quality into a system (1 mark). They provide assurance that standards of completeness and accuracy are enforced for each individual record or business transaction (1 mark). Other sensible answer should also receive credit.
(b)	List three specific needs which controls help to enforce.	[3]
	One mark should be awarded for each valid point (up to a maximum of three marks). Examples include the following: Accuracy. Integrity. Confidentiality. Other sensible answer should also receive credit.
(c)	Describe the use of data entry controls in the following types of system:	[2]
	(i) Batch processing systems.	[2]
	In the context of batch processing systems, data entry controls are designed to ensure the accuracy of typing and completeness of records (1 mark). An edit run involves balancing totals for each control field against those entered from the batch header; further processing can take place only if these balance (1 mark). Other sensible answer should also receive credit.
	(ii) Real-time systems.
	In the context of real-time systems, each input transaction is released immediately for further processing by the system (1 mark). Input control must be applied to one document at a time; for example, a typical technique might rely on visual verification (1 mark). Other sensible answer should also receive credit.
(d)	Describe the following types of control:
	(i) Communication controls.	[2]
	Communication controls, such as the use of encryption, help assure the security and confidentiality of data (1 mark). For example, data is encoded prior to transmission and decoded after transmission (1 mark). Other sensible answer should also receive credit.
	(ii) Audit trails.	[2]
	The application of audit trails can help assure the integrity, reliability, and accuracy of data (1 mark). An audit trail is simply a series of records that can be used for tracking data from prior to a transaction to when the data is incorporated into a master file (1 mark). Other sensible answer should also receive credit.
	(iii) Output controls.	[2]
	Output controls are the final quality assurance measures that can be applied to data (1 mark). It should be essential that output report totals can always be compared to input control totals (1 mark). Other sensible answer should also receive credit.
(e)	Describe the purpose of the following types of documentation:
	(i) System and program documentation.	[1]
	System and program documentation is maintained for use in system maintenance. Other sensible answer should also receive credit.
	(ii) Operations documentation.	[1]
	Operations documentation is maintained to describe all operating procedures. Other sensible answer should also receive credit.
	(iii) User documentation.	[1]
	User documentation is maintained to guide users in how to use the system and make use of results produced by it. Other sensible answer should also receive credit.
(f)	Why is it important to update documentation to reflect current procedures each time a change to the documented system is made?	[2]
	Computer information systems are dynamic: change is a regular occurrence (1 mark). If documentation is not updated to reflect changes, then erroneous processing may take place, or users may follow instructions which are no longer appropriate (1 mark). Other sensible answer should also receive credit.