December 1999
SD206 : SYSTEMS DESIGN

QUESTION 1 (Compulsory)

Total Marks: 30 Marks

• Question 2
• Question 3
• Question 4
• Question 5
• Cover Page

SUGGESTED SOLUTIONS
Solutions and allocated marks are indicated in green.
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Describe three characteristics exhibited by real-time systems.
One mark should be awarded for each valid point,with a further mark added for each satisfactory elaboration (up to a maximum of six marks).Examples include the following:

•Process orientation (1 mark).Data is processed on a continuous basis,in contrast to the processing ofdata on a periodic basis as is the case for batch processing systems (1 mark).

•On-line file availability (1 mark).The database is on-line and available to users at all times for interacting,querying,and updating (1 mark).

•Very short time intervals (1 mark). Real-time processing eliminates the time interval between the point at which users query the system or enter transactions and the time at which the system processes the queries or transactions (1 mark).

•Constant updating (1 mark).When a transaction which requires a change to the master file occurs,a record is accessed from the file,updated,and written back;the original value is lost (1 mark).

•Organisation of records for rapid access (1 mark).Records are stored and processed using direct access (1 mark).

Other valid answers should also receive credit.

(i)What are controls ?[2 marks ]
Controls are functions (1 mark)that are designed to build the required level of quality into a system (1 mark).
Other valid answers should also receive credit.

(ii)Why are controls needed?[1 mark ]
Controls are needed for quality assurance.

(iii)List three needs met by controls.[3 mark ]
One mark should be awarded for each of the following points. •Accuracy.
•Integrity.
•Confidentiality.

Name three broad classes of maintenance and,in each case,list one type of maintenance activity which might appear in that class.
For each of the following,one mark should be awarded for naming the class and a further mark should be awarded for a suitable example.

•Corrective maintenance (1 mark).Examples include emergency fixes and routine debugging (1 mark).

•Adaptive maintenance (1 mark).Examples include accommodation of changes to data or files,to hardware,or to software (1 mark).

•Perfective maintenance (1 mark).Examples include user enhancement and improved documentation (1 mark)

(i)List two benefits associated with CASE technology.[2 marks ]
One mark should be awarded for each benefit named (up to a maximum of two marks).Examples include the following:

•Easing revision ofapplications.
•Support ofprototyping.
•Code generation.
•An improved ability to meet user requirements.
•The support of an iterative development process.

(ii)List two drawbacks associated with CASE technology.[2 marks ]
One mark should be awarded for each drawback named (up to a maximum of two marks).Examples include the following:

•A reliance on structured methods.
•An absence ofstandard levels ofmethodology support.
•Diagrams are not used.
•Limited function.
•Limited scope.
•Human tasks remain critical.

(i)Define the term system test .[2 marks ]
A system test is a test of the entire system using live data (1 mark)in an attempt to examine all processing situations under typical conditions (1 mark).
Other valid answers should also receive credit.

(ii)What does the operations group do during a system test?[1 mark ]
The operations group attempts to run the system in compliance with the operations documentation.

(iii)List two major objectives ofsystem testing.[2 marks ]
One mark should be awarded for each valid point (up to a maximum of two marks).Examples include the following:

•To perform a final test of all programs against the design specifications.
•To ensure that the operations group has adequate documentation and instructions to operate the system properly,process the incoming data, and distribute outgoing information from the system.
•To guarantee that the end users can successfully interact with the system.
•To test the backup and restart capabilities ofthe system to be sure that they are adequate under actual processing conditions.
•To verify that all system components are correctly integrated,so data and information flow smoothly between departments and through the system within predicted time requirements.
•To confirm that the system can handle normal production volumes of data in a timely and responsive manner.
Other valid answers should also receive credit.

(iv)Why are final system tests often called acceptance tests ?[1 mark ]
Final system tests are often called acceptance tests because the successful completion of system testing is the key factor in end user and management acceptance ofthe developed system
Other valid answers should also receive credit.

(v)What should be highlighted in a presentation to management following system testing?[2 marks ]
One mark should be awarded for each valid point (up to a maximum of two marks).Examples include the following:

•The system test results.
•The status of all ofthe required documentation.
•The users ’opinions regarding the quality and acceptability of the new system.
Other valid answers should also receive credit.