Objectives: Introduction Over View of System Analysis and Design
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- 8.10 System controls
| 8.9 Testing Libraries To assure that all systems are properly tested, many organizations establish test libraries. A testing library is a set of data developed to thoroughly test a system of programs. It is stored in machine – readable form, usually on magnetic disk, and is used by all persons who are involved with a particular system. For example, a large inventory system consists, of hundreds of computer programs. All share common data and file formats. Each will also process similar transactions and will sometimes update records and other times retrieve data to respond to inquiries or prepare reports and documents. Because these programs are interdependent and process – related transactions, it makes sense to use a common set of data to test each program. Test libraries are not just for initial testing. As the system evolves and programs are modified and maintained, they must be retested. The testing library should be maintained throughout the life of the system so that, as each change is made, reliable data are again available to test the system. 8.10 System controls A well-designed system should have controls to ensure proper operation and routine auditing. A candidate systems failure often results from lack of emphasis on data control. Therefore, standards of accuracy, consistency and maintainability must be specified to eliminate errors and control for fraud. A system design introduces new control elements and changes the control procedures. New controls in the form of relational comparisons are designed to detect and check errors that rise form the use of the system. Ina manual system, internal control depends on human judgement, personal care and division of labor. Ina computer based system the number of persons involved is considerably reduced. In designing anew system the designer should specify the location of error control points and evaluate them on the basis of error frequency, cost and timing of error detection. By identifying points where potential errors may occur, designers can create control procedures for handling errors immediately. Download 0.94 Mb. Share with your friends:
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