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6.5 Data Flow Anomalies

Data flow anomalies are two-character sequence of actions, namely, defined (d), killed (k), or used (u). Thus we can have nine two-letter combinations: dd, dk, du, kd, kk, ku, ud, uk, uu. When such activities are occurring, the possibilities of bugs or no bugs are as shown in Fig. 6.2 Two-letter Combinations and Possibility of Anomaly.

Fig. 6.2 Two-letter Combinations and Possibility of Anomaly

In addition to the above two-letter situations, there are six single letter situations with preceding dash or succeeding dash. Preceding dash with letters d, k, u indicate that nothing special occurs prior to the action along the entry-exit path considered. Succeeding dash with letters d, k, u indicate that nothing special occurs after the action along the entry-exit path considered. Meaning of six single letter situations with preceding dash or succeeding dash are explained below in Fig. 6.3 Single-letter Combinations and Possibility of Anomaly:
Fig. 6.3 Single-letter Combinations and Possibility of Anomaly

Single – letter situations do not provide clear cut existence of data flow anomalous, however with appropriate intuitions the tester can infer the possibility of data flow anomalous.
 
 
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