System Analysis and Design

191. By levelling a DFD we mean

1. splitting it into different levels
2. make its structure uniform
3. expanding a process into one with more sub-processes giving more detail
4. summarizing a DFD to specify only the essentials

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192. When a DFD is levelled

1. new external entities may be required
2. no new processes are allowed
3. no new data flows are allowed
4. new data stores may be necessary and are allowed

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193. A physical DFD

1. has no means of showing material flow
2. does not concern itself with material flow
3. can show only stored material
4. can show the flow of material

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194. A data store in a DFD represents

1. a sequential file
2. a disk store
3. a repository of data
4. a random access memory

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195. When a DFD is levelled it is a good idea not to

1. be concerned about the number of new processes at the next level
2. allow more than 5 to 10 new processes at the next level for each expanded process
3. allow new data stores at the next level
4. allow any new processes at the next level

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196. External Entities may be a

1. source of input data only
2. source of input data or destination of results
3. destination of results only
4. repository of data

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197. A context diagram is used

1. as the first step in developing a detailed DFD of a system
2. in systems analysis of very complex systems
3. as an aid to system design
4. as an aid to programmers

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198. A data flow can

1. only enter a data store
2. only leave a data store
3. enter or leave a data store
4. either enter or leave a data store but not both

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199. When a DFD is levelled no new

1. data stores may appear
2. external entities may appear
3. processes may appear
4. data flows may appear

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200. Structured English is used to describe

1. how programs are to be written
2. processes in a DFD in a reasonably precise manner
3. how DFDs are used in data processing
4. data flows in DFD

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