GATE | GATE-CS-2009 | Question 49

Which of the following statements are TRUE?

• I. The context diagram should depict the system as a single bubble.
• II. External entities should be identified clearly at all levels of DFDs.
• III. Control information should not be represented in a DFD.
• IV. A data store can be connected either to another data store or to an external entity.

(A)

II and III

(B)

II and III

(C)

I and III

(D)

I, II and III

Answer: (C)

Explanation:

Only statement (I) and (III) are correct. 

Statement (II) is not correct, because all external entities interacting with the system should be represented only in context diagram. The external entities should not appear in the DFDs at any other level. 

Statement (IV) is not correct, because a DFD represents only data flow, and it does not represent any control information. 

So, option (C) is true.

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