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Algorithms

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Question 3

An automated aquarium life-support system uses the following algorithm to monitor water parameters and control actuators, but it does not make efficient use of selection structures.

1   WHILE (monitorActive = True) DO
2
3       RECEIVE phSensor FROM PH_SENSOR
4       IF (phSensor > 8.2) THEN
5           SET acidDoseStatus TO "On"
6       END IF
7
8       RECEIVE salinitySensor FROM SALINITY_SENSOR
9       IF (salinitySensor < 32.0) THEN
10          SET saltDoseStatus TO "On"
11      END IF
12
13      RECEIVE dissolvedOxygenSensor FROM DO_SENSOR
14      IF (dissolvedOxygenSensor < 6.5) THEN
15          SET aeratorStatus TO "On"
16      END IF
17
18      IF (phSensor <= 8.2) THEN
19          SET acidDoseStatus TO "Off"
20      END IF
21
22      IF (salinitySensor >= 32.0) THEN
23          SET saltDoseStatus TO "Off"
24      END IF
25
26      IF (dissolvedOxygenSensor >= 6.5) THEN
27          SET aeratorStatus TO "Off"
28      END IF
29
30  END WHILE

Write replacement code to control the aquarium aerator (aeratorStatus) that would improve the efficiency of this algorithm.

[2]
Markscheme

Algorithms Questions

  1. GCSE
  2. /Computer Science
  3. /Algorithms

159 exam-style questions on Edexcel GCSE Computer Science Algorithms, covering Constructs for solving problems, Variables, constants and data structures, Arithmetic, relational and logical operators, Tracing algorithm output with trace tables, Types of error and correcting logic errors, Standard algorithms (sorts and searches), and Evaluating algorithm fitness and efficiency. Each one has a worked solution and a mark scheme showing where the marks go.

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