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Programming constructs reactivation

This later-course reactivation joins familiar constructs into one program. Sequence fixes order, selection chooses a path, and iteration repeats. A one-dimensional structure stores an ordered set of items. The examination expects you to read, trace, debug and construct programs—not merely name the constructs.

1. Model a complete data-processing pattern

scores = [12, 8, 15, 6]
total = 0
high_count = 0
for score in scores:
    total = total + score
    if score >= 10:
        high_count = high_count + 1
print(total)
print(high_count)

The loop visits each list item once. The accumulator total changes every pass. high_count changes only when selection is true. Reading by state change is more reliable than guessing from the final print lines.

Fill in the blanks3 marks

The assignment statements run in gap 1. The if statement performs gap 2. The for loop performs gap 3 through a one-dimensional structure.

iteration
selection
sequence
validation

2. Predict before execution

Read this code without running it.

values = [3, 7, 2]
total = 0
for value in values:
    if value > 3:
        total = total + value
    else:
        total = total + 1
print(total)

Multiple choice1 mark

What exact value is printed?

Written answer2 marks

Explain how the program reaches the printed value.

Describe all three iterations and the branch used.

Students type their answer here.

Trace table5 marks

Complete the trace table for this count-and-total algorithm.

Record changes to item, total and passes on every iteration.

Use one row for each pass through the loop. Fill in a box only when that value changes on that row, and leave the rest blank.

ProgramPython

items = [4, 1, 6]
total = 0
passes = 0
for item in items:
total = total + item
passes = passes + 1
print(total)
print(passes)

Trace table with 5 columns
Row	items	total	passes	item	Output
1
2
3
4
5
6
7

3. Choose the loop that matches the problem

Use a for loop when traversing every item in a known structure or a known range. Use a while loop when repetition depends on a condition, such as asking again while input remains invalid. The condition must be able to become false; otherwise the loop may never terminate.

Multiple choice1 mark

A program must keep asking until a PIN has exactly four digits. Which construct best controls the repetition?

AA single `if`
BA `while` loop
CA list assignment
DAn `elif` with no `if`

Written answer2 marks

A loop contains while attempts < 3: but never changes attempts. Identify the likely error and describe the correction.

Connect the unchanged control variable to termination.

Students type their answer here.

4. Construct an integrated solution

Complete a program that visits every value in temperatures. It must total all values and count values at least 20. Store the count in warm_count, store the total in total, and print both values on separate lines.

Coding task5 marks

temperatures = [18, 22, 20, 16, 25]
# Total the values and count values at least 20.

Multiple choice1 mark

Which claim about iterating for item in items is correct?

AIt changes every list item automatically.
BIt visits each item in order without needing an index variable.
CIt can run only when the list contains strings.
DIt always repeats forever.

Route forward

You have reactivated sequence, selection, repetition and one-dimensional traversal. Next you will organise these constructs inside parameterised subprograms and control the scope of names.