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Algorithms

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Question 34

An automated greenhouse ventilation system uses the following algorithm to control sensors and actuators, but it does not make efficient use of selection structures.

1   WHILE (systemActive = True) DO
2
3       RECEIVE tempSensor FROM TEMP_SENSOR
4       IF (tempSensor > 25) THEN
5           SET fanStatus TO "On"
6       END IF
7
8       RECEIVE humiditySensor FROM HUMIDITY_SENSOR
9       IF (humiditySensor < 40) THEN
10          SET misterStatus TO "On"
11      END IF
12
13      RECEIVE lightSensor FROM LIGHT_SENSOR
14      IF (lightSensor < 200) THEN
15          SET lightStatus TO "On"
16      END IF
17
18      IF (tempSensor <= 25) THEN
19          SET fanStatus TO "Off"
20      END IF
21
22      IF (humiditySensor >= 40) THEN
23          SET misterStatus TO "Off"
24      END IF
25
26      IF (lightSensor >= 200) THEN
27          SET lightStatus TO "Off"
28      END IF
29
30  END WHILE

Write replacement code to control the greenhouse fan (fanStatus) 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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