Tracing and fixing a broken flowchart · Year 7 Thinking like a computer scientist, lesson 5 · KS3 Computing

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Tracing and fixing a broken flowchart (assessed)

Year 7 · Thinking like a computer scientist · Lesson 5 of 5Mixed

What you'll learn

Trace a flowchart with test data to find the output
Find and fix errors in a flowchart
Turn a fixed flowchart into a working Python program and test it

Open the slides

Extra resources

Raspberry Pi Code Editor (Python in the browser, no install)

Tracing and fixing a broken flowchart (assessed)

Year 7 · Thinking like a computer scientist · Lesson 5 of 5Mixed

NameFormDate

Trace and fix a flowchart

A. Trace the cinema flowchart (6 marks)

How this task is marked (out of 20).

Section	What earns marks	Marks
A	Correct outputs in the trace table, plus the explanation	6
B	Finds both bugs, explains them and fixes them	8
C	Working Python that matches the fixed flowchart, tested with all three inputs	6

This flowchart works out a cinema ticket price.
Box Shape Text Next
1 Terminator START 2
2 Input/output INPUT age 3
3 Decision Is age < 12? Yes: 4, No: 5
4 Process price ← 5 6
5 Process price ← 8 6
6 Input/output OUTPUT price 7
7 Terminator STOP
Trace the flowchart for each age.
age Is age < 12? Boxes visited Output
8
12
15
A pupil who is exactly 12 says the price is unfair. Explain why they pay 8.

B. Find and fix the bugs (8 marks)

This flowchart should output Pass for a test score of 30 or more out of 50, and Fail otherwise. It has two bugs.
Box Shape Text Next
1 Terminator START 2
2 Input/output INPUT score 3
3 Decision Is score > 30? Yes: 4, No: 5
4 Input/output OUTPUT "Fail" 6
5 Input/output OUTPUT "Pass" 6
6 Terminator STOP
Trace it with the test data and compare with what should happen.
score Expected output Actual output Correct?
35
30
12
Describe the two bugs.
Write the corrected text for any boxes you need to change.

C. Test it in Python (6 marks, on computers)

Write the fixed flowchart in Python. Start with this line:
```
score = int(input("Enter your score: "))
```
Run your program with each test score and record the results.
score Expected output Actual output
35 Pass
30 Pass
12 Fail
Explain why testing with 30 is important for this program.

Box	Shape	Text	Next
1	Terminator	START	2
2	Input/output	INPUT age	3
3	Decision	Is age < 12?	Yes: 4, No: 5
4	Process	price ← 5	6
5	Process	price ← 8	6
6	Input/output	OUTPUT price	7
7	Terminator	STOP

age	Is age < 12?	Boxes visited	Output
8
12
15

score	Expected output	Actual output	Correct?
35
30
12

score	Expected output	Actual output
35	Pass
30	Pass
12	Fail

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