Computer Science code builder

The code builder makes GCSE code tracing questions without running any code. Pick a construct and the tool assembles a short snippet from parts with a known result, so the output is guaranteed, then shows it as AQA pseudocode, OCR Exam Reference Language or Python. Ask the class to predict the output, find the planted bug or complete the trace table.

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Code Builder

State the output of this code.

1total ← 0
2FOR i ← 1 TO 6
3    total ← total + i
4ENDFOR
5OUTPUT total

total = 0
for i in range(1, 7):
    total = total + i
print(total)

total ← 0
FOR i ← 1 TO 6
    total ← total - i
ENDFOR
OUTPUT total

total = 0
for i in range(1, 7):
    total = total - i
print(total)

numbers ← [3, 3, 4, 3]
total ← 0
FOR i ← 0 TO LEN(numbers) - 1
    n ← numbers[i]
    total ← total + n
ENDFOR
OUTPUT total

numbers = [3, 3, 4, 3]
total = 0
for n in numbers:
    total = total + n
print(total)

numbers	total	n	Output
[3, 3, 4, 3]	0
	3	3
	6	3
	10	4
	13	3	13

Adds the whole numbers from 1 to 6 and prints the running total.

A hand-built replica of the real builder page, not a screenshot. Every control shown exists in the product.

Also available in this tool, OCR Exam Reference Language and AQA pseudocode trace tables.

Why this works in Computer Science

The snippet above is a for loop, the construct every board examines first. One click flips it between AQA pseudocode and Python, and the same loop becomes a find the bug task with one planted error, or a trace table with the first row filled in for the class to continue. Nothing is executed. The code is built by construction, so the answer on the board is right every time.

Exam pseudocode is where pupils drop marks, because each board writes it differently. Set the board and the syntax follows the specification, so the class practises reading the notation they will meet in the paper, and Python is there for anyone teaching the language itself. In the presenter you step through the trace one line at a time, offer a hint, then reveal the answer once the class has committed.

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