August
1997 QUESTION 4 Total Marks: 20 Marks |
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questions
SUGGESTED SOLUTIONS |
| 4. | Describe the seven steps involved in the transformation of a data flow diagram with transaction flow characteristics to a program structure representation. | [7] | |
| 1. | Review the fundamental system model | ||
| 2. | Review and refine DFD for the software | ||
| 3. | Determine whether the DFD has transform or transaction flow characteristics | ||
| 4. | Identify the transaction centre and the flow characteristics along each of the action paths | ||
| 5. | Map the DFD into program structure of each action path | ||
| 6. | Factor and refine the transaction structure of each action path | ||
| 7. | Refine the 'first-cut' program structure using design heuristics for improved software quality | ||
| one mark for each step | |||
| [7 marks] | |||
| (b) With the use of an appropriate diagram, explain what is meant by structures that have a degree of fan in and fan out. | [3] | ||
| diagram: study guide p-6-20 | |||
| fan-in: measures the number of modules that directly control a given module | |||
| fan-out: measures the number of modules that are directly controlled by a given module | |||
| one mark for each step | |||
| [3 marks] | |||
| (c) Data structure-oriented design methods are a broad class of methods used in design. Describe briefly what such methods use in their derivation of design. | [2] | ||
| method focuses on the information design | [1] | ||
| uses information structure as the main foundation for the derivation of design | [1] | ||
| [2 marks] | |||
| (d) One such data structure-oriented design method is Jackson's Structured Programming. Describe the steps involved in this technique. | [8] | ||
| 1. | Draw structure diagrams for each set of data, so that the structure reflects the way in which the data is to be processed | ||
| 2. | Identify points of correspondence of a one-for-one nature between components of individual data structures | ||
| 3. | Produce a program structure diagram using the same notation as that used in data structures, combining them at points of correspondence | ||
| 4. | For each iteration and selection appearing in the program structure diagram, construct appropriate conditions | ||
| 5. | Examine the specification and the conditions, and from them construct a list of basic program operations in plain language | ||
| 6. | Allocate the conditions and operations to the appropriate components of the program structure | ||
| 7. | Produce schematic code, also known as pseudo-code, from the program structure | ||
| 8. | Implement the pseudo-code in a target high-level programming language | ||
| 1 mark for each step. Since it is possible to combine some of the above steps, careful reading of candidates' answers may be necessary | |||
| [8 marks] | |||